high rpm miss

PakstinN

Member
Jul 17, 2014
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hello all, lately I have been battling a high rpm miss in my car. she is a 1991 lx 5.0, fresh 306, ed Curtis cam, prepped p heads (ported and bigger valves). this miss seems to only occur at wot and above 4000 rpm, if my foot isn't in it as hard, it doesn't seem to miss. I can make a 3/4 throttle pull straight up to 6k but if I put it all the way to the floor it has a miss in it. the car has a brand new fuel pump, fuel filter, plugs, wires, and distributor. I have now went through 2 distributors and 3 tfi modules with no success. anyone had a similar problem? any ideas what my next option should be?
 
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08GT500

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Jul 12, 2018
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As I don’t know what all Mod’s are, didn’t mention if it’s running EFI or Carbureted. I’m going with EFI and running the EEC, and going to try and base this on theory. Is the Car running an EEC Tune? Any CEL or Codes in EEC? If you can get to the higher RPM’s by using less pedal, you can likely rule out a Spark quality Condition issue as it would not ever hit 6 Grand. I’d be looking at a possible A/F ratio issue, is everything able to breathe at the Motor seems I be set up to, at WOT ?
 

PakstinN

Member
Jul 17, 2014
82
16
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my bad, its running an explorer intake, 70mm throttle body and spacer, stock maf (looking into that as a possible issue), runs eec-iv with a 4 bank chip and tunes done by bama. the thing that really bothers me is that when the motor was just put in and past break in, it ran perfectly fine. I changed oil on it one day and when I pulled it out of the shop it has never been the same since, it had a miss in it that made it nearly undrivable I ended up finding a bad tfi module and when I replaced it, it went from barely being able to run (timing advance obviously being fubared) to being totally drivable until I really lay my foot in it.
 

08GT500

Active Member
Jul 12, 2018
904
140
53
52
Massachusetts
my bad, its running an explorer intake, 70mm throttle body and spacer, stock maf (looking into that as a possible issue), runs eec-iv with a 4 bank chip and tunes done by bama. the thing that really bothers me is that when the motor was just put in and past break in, it ran perfectly fine. I changed oil on it one day and when I pulled it out of the shop it has never been the same since, it had a miss in it that made it nearly undrivable I ended up finding a bad tfi module and when I replaced it, it went from barely being able to run (timing advance obviously being fubared) to being totally drivable until I really lay my foot in it.
Hi again, John BTW. Yes- you highly likely need to get an aftermarket MAF sensor, 91’s had a 55mm Stock Intake diameter- now at 70mm, with a Built Motor- (Not privy to your Cam Spec’s) but increased Cam overlap, Duration, Lift- running 1.7 Rockers, or 1.6’s? (Hope you’re not running the Explorer GT40 Heads- they won’t flow past 0.500 Valve lift unless ported. Stock GT40P Springs will Coilbind at about 0.480 lift- many Motors setup like this live ONLY because the Hydraulic Roller lifters absorb the excess lift, Pushrods don’t bend- short and hardened. A SOLID Roller Cam would wipe out the Pushrods when you’re rolling over the Motor by the Crank setting Lash. But, If a Shop built this- they would have given you Springs/Retainers/Keepers to give you 0.060 MIN V.SpringCoil separation, at full Valve lift. & a
P to V clearance test. Those Heads are good- some just overdo it, is all.
My point is that your’e pulling more Air than the Stock MAF can likely handle, you’re not @19lb Injectors, either (Stock)-correct? You need to match to MAF to Injector size, YES- it can be done within a Tune, but likely exceeded by the abilities of the MAF you’re running. Running what you need, you’re Motor will behave much better- mileage increase, AND run MUCH Stronger!
An Air/Fuel mixture gauge is a useful Gauge to have, as is a Manual Oil pressure Gauge-especially with a new Motor.. I’ve done this for 30yrs, Tuned for 17.(Small talk another day). You put lots of Coin into this- see it through, get ALL the Motor you paid for- right? You’re on the right track- don’t stop..Things you need to get this right Cost $, but pale in comparison to what you’d likely spent- and just as important as the Machine Shop correctly nailing the tolerances in your 306. That in mind, Fox issues are Occam's Razor, 99%..You got this. So #1- Oil, the Viscosity the same, didn’t swap to another Type? (Some types/Viscosity changes can cause lifter pump up @ high RPM’s- is rare, but occurs. Blowby increases). You may have disturbed a Vacuum line, Ground, etc. Your issue I’d bet is a simple one. Usually Sensors, Wires, Connectors, Grounds..First- if not already, pull your EEC Codes. Have a Scantool/reader. If not, not a huge Cost. I’d think you may have a Vacuum leak, Ground issue (Connector, possibly- Motors just installed tend to find any spot to chafe coating off a wire, vacuum line, etc. most common time for this to occur). You need to reset your TPS. Or, your MAF Sensor- quick Test, pull the MAF Plug, engine Running. Motor should die- or run very badly. Red Flag if not. Pull it, Clean it. Check for greasy residue inside your CAI. Clean it all out if so, your Sensors, and If you’re running a tall filler tube Passenger side Valve Cover, & running a line to your CAI direct from that upper neck- Plug them both off if you spot residue. You already have a PCV Valve, this can make the potential MAF sensor insufficiency worse. What are you running for a Coil, try a spare? going through an aftermarket Ignition like an MSD? You had checked your Plugs since the Ignition issue- yes? If not since- an excellent guideline. Take it for the rip- close to home, Read them. Black is Rich, White is evidence of high temps, cracked insulator- high electrode wear is Detonation (Timing too far Advanced- Octane level too low). Oily (inside the Plug) is Rings not seated, Valve Seal leaks, Tan is optimal. Despite all I’d said, I mean only respect, and have the will to help. God, I’ve been there, lol! Look to the easiest- most logical, that’s likely the culprit. Pop the Car back up and look for a possible issue caused at that point. It could be coincidence- but follow the events, as occurred in time.
Funny at first- then It becomes pathetic to see “that guy” at a Parts Store that buys a bunch of sensors, no clue- and a buddy finds a simple vacuum leak. The EEC MAF codes are either 66 or 25.
Do you mind giving a little more info on your build? How far Has the Motor been broken in for completely, how many miles? What Compression ratio are you running? Cam Spec’s? Plugs you’re running?You have the same issue with each BAMA Tune you select- anything get WORSE with the less radical tunes, will it still run on the STOCK Tune?Timing advanced at about 11-12 Degrees with the SPOUT removed? Your Air Filter Super Clean and very, very slightly Oiled? Are you running GT40 or GT40P Heads- Shop set everything up? I’ll help you as much as necessary- I’m not sure how privy you are to these- NOT insulting your intelligence, regardless of experience. Just listing fact regarding what I’ve learned to be true, and experienced. I Work 6-12’s, out at Midnight. What a Shift, lol! I’ll check tomorrow- see how you made out, see if you left Info. Good Luck!
 

08GT500

Active Member
Jul 12, 2018
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My 08’ Shelby GT500, and an 89’ Cobra I’m repairing many serious misconceptions regarding Valvetrain, Fuel System Tuning and Ignition by its Owner- on the side. Not as much of a fan of what Ford’s done to the newer line. Shelby tips the scales at 10.10’[email protected] 127 on 315’s, now. Still breaking loose right to around 800 Foot mark. The Car has 18K on it. Not a scratch on it, OEM Motor is right where it belongs- SuperSnake lowered Suspension, 4” Aluminum Driveshaft-Loops, highly detailed undercarriage- but otherwise just a “tweaked” Stock 5.4l with some lopey Cams, Ported Eaton Huffer w 2.4” Pulley, OD Crank Pulley Boosting 21 Lbs, 90lb Injectors, yada, Yada.. Stock looking- Passes Emissions with an accelerometer Documented 700HP -800Ft/Lbs at the Wheels, (Dyno this August) a real handful on the Street..8 progressiveTunes it Stores and runs. 1 is Emissions Legal.
 

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08GT500

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08’ GT500 & 96’ Cobra.
 

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PakstinN

Member
Jul 17, 2014
82
16
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24
Hi again, John BTW. Yes- you highly likely need to get an aftermarket MAF sensor, 91’s had a 55mm Stock Intake diameter- now at 70mm, with a Built Motor- (Not privy to your Cam Spec’s) but increased Cam overlap, Duration, Lift- running 1.7 Rockers, or 1.6’s? (Hope you’re not running the Explorer GT40 Heads- they won’t flow past 0.500 Valve lift unless ported. Stock GT40P Springs will Coilbind at about 0.480 lift- many Motors setup like this live ONLY because the Hydraulic Roller lifters absorb the excess lift, Pushrods don’t bend- short and hardened. A SOLID Roller Cam would wipe out the Pushrods when you’re rolling over the Motor by the Crank setting Lash. But, If a Shop built this- they would have given you Springs/Retainers/Keepers to give you 0.060 MIN V.SpringCoil separation, at full Valve lift. & a
P to V clearance test. Those Heads are good- some just overdo it, is all.
My point is that your’e pulling more Air than the Stock MAF can likely handle, you’re not @19lb Injectors, either (Stock)-correct? You need to match to MAF to Injector size, YES- it can be done within a Tune, but likely exceeded by the abilities of the MAF you’re running. Running what you need, you’re Motor will behave much better- mileage increase, AND run MUCH Stronger!
An Air/Fuel mixture gauge is a useful Gauge to have, as is a Manual Oil pressure Gauge-especially with a new Motor.. I’ve done this for 30yrs, Tuned for 17.(Small talk another day). You put lots of Coin into this- see it through, get ALL the Motor you paid for- right? You’re on the right track- don’t stop..Things you need to get this right Cost $, but pale in comparison to what you’d likely spent- and just as important as the Machine Shop correctly nailing the tolerances in your 306. That in mind, Fox issues are Occam's Razor, 99%..You got this. So #1- Oil, the Viscosity the same, didn’t swap to another Type? (Some types/Viscosity changes can cause lifter pump up @ high RPM’s- is rare, but occurs. Blowby increases). You may have disturbed a Vacuum line, Ground, etc. Your issue I’d bet is a simple one. Usually Sensors, Wires, Connectors, Grounds..First- if not already, pull your EEC Codes. Have a Scantool/reader. If not, not a huge Cost. I’d think you may have a Vacuum leak, Ground issue (Connector, possibly- Motors just installed tend to find any spot to chafe coating off a wire, vacuum line, etc. most common time for this to occur). You need to reset your TPS. Or, your MAF Sensor- quick Test, pull the MAF Plug, engine Running. Motor should die- or run very badly. Red Flag if not. Pull it, Clean it. Check for greasy residue inside your CAI. Clean it all out if so, your Sensors, and If you’re running a tall filler tube Passenger side Valve Cover, & running a line to your CAI direct from that upper neck- Plug them both off if you spot residue. You already have a PCV Valve, this can make the potential MAF sensor insufficiency worse. What are you running for a Coil, try a spare? going through an aftermarket Ignition like an MSD? You had checked your Plugs since the Ignition issue- yes? If not since- an excellent guideline. Take it for the rip- close to home, Read them. Black is Rich, White is evidence of high temps, cracked insulator- high electrode wear is Detonation (Timing too far Advanced- Octane level too low). Oily (inside the Plug) is Rings not seated, Valve Seal leaks, Tan is optimal. Despite all I’d said, I mean only respect, and have the will to help. God, I’ve been there, lol! Look to the easiest- most logical, that’s likely the culprit. Pop the Car back up and look for a possible issue caused at that point. It could be coincidence- but follow the events, as occurred in time.
Funny at first- then It becomes pathetic to see “that guy” at a Parts Store that buys a bunch of sensors, no clue- and a buddy finds a simple vacuum leak. The EEC MAF codes are either 66 or 25.
Do you mind giving a little more info on your build? How far Has the Motor been broken in for completely, how many miles? What Compression ratio are you running? Cam Spec’s? Plugs you’re running?You have the same issue with each BAMA Tune you select- anything get WORSE with the less radical tunes, will it still run on the STOCK Tune?Timing advanced at about 11-12 Degrees with the SPOUT removed? Your Air Filter Super Clean and very, very slightly Oiled? Are you running GT40 or GT40P Heads- Shop set everything up? I’ll help you as much as necessary- I’m not sure how privy you are to these- NOT insulting your intelligence, regardless of experience. Just listing fact regarding what I’ve learned to be true, and experienced. I Work 6-12’s, out at Midnight. What a Shift, lol! I’ll check tomorrow- see how you made out, see if you left Info. Good Luck!

first of all, thank you John for taking the time to type out such a thorough response. as for the extra information on the build, the motor was broken in using conventional oil with zinc additive at first, ran her for roughly 50 very nice easy miles then changed oil, ran conventional oil again (was told that conventional oil is better for making sure rings seat) anyways, after changing the oil again we ran her through some rpm cycles, not very aggressive on the throttle at all, but slowly gave the motor some rpm and let the rpms wind down, took it easy for roughly 500 miles, changed oil again and made a few pulls, mostly easy driving, then after around total miles, changed oil again. the engine got a 600-700 mile break in. she runs 9.0:1 compression, the cam specs are .555/.558 lift 224/220 @ .050, 111 lobe separation. I am currently running regular automate 104 spark plugs (although I normally try and run at least an autolite platinum or better).I haven't tried making any pulls with the chip on tune 2 or 3, may have to try that and see what happens. when I put the chip on tune 0 (assuming that would be the stock a9l tuning, no it doesn't really run. I have checked the timing and it is set at 14*, have not tried unplugging the mass air meter yet, I have a new air filter on the way as I am not totally satisfied with its current condition. I am running gt40p heads that have bigger valves and have been ported. the heads were tested on a flow bench to 239 [email protected] .500 lift, the springs I used are Alex's parts springs (I double and triple checked with ed Curtis that the springs and cam would work together, which he said they would), admittedly I am not very handy with diagnosing problems like this, I don't even own a scan tool for etc-iv. I personally am growing more and more suspicious that I possibly am having an ignition switch go out, went to the car yesterday afternoon and she wouldn't start at all..went to her today now and she cracked right off.
 

08GT500

Active Member
Jul 12, 2018
904
140
53
52
Massachusetts
first of all, thank you John for taking the time to type out such a thorough response. as for the extra information on the build, the motor was broken in using conventional oil with zinc additive at first, ran her for roughly 50 very nice easy miles then changed oil, ran conventional oil again (was told that conventional oil is better for making sure rings seat) anyways, after changing the oil again we ran her through some rpm cycles, not very aggressive on the throttle at all, but slowly gave the motor some rpm and let the rpms wind down, took it easy for roughly 500 miles, changed oil again and made a few pulls, mostly easy driving, then after around total miles, changed oil again. the engine got a 600-700 mile break in. she runs 9.0:1 compression, the cam specs are .555/.558 lift 224/220 @ .050, 111 lobe separation. I am currently running regular automate 104 spark plugs (although I normally try and run at least an autolite platinum or better).I haven't tried making any pulls with the chip on tune 2 or 3, may have to try that and see what happens. when I put the chip on tune 0 (assuming that would be the stock a9l tuning, no it doesn't really run. I have checked the timing and it is set at 14*, have not tried unplugging the mass air meter yet, I have a new air filter on the way as I am not totally satisfied with its current condition. I am running gt40p heads that have bigger valves and have been ported. the heads were tested on a flow bench to 239 [email protected] .500 lift, the springs I used are Alex's parts springs (I double and triple checked with ed Curtis that the springs and cam would work together, which he said they would), admittedly I am not very handy with diagnosing problems like this, I don't even own a scan tool for etc-iv. I personally am growing more and more suspicious that I possibly am having an ignition switch go out, went to the car yesterday afternoon and she wouldn't start at all..went to her today now and she cracked right off.[/QUOTE
Hi! Good to hear from you. There’s a few things that I think may help you out- and NO PROBLEM! Correct with the Oil and seating Rings. Never use Synthetic initially-or they may glaze over- especially the harder ‘Moly’ Piston Rings. Btw-Did you you use Heat Sink Compound when you reinstalled the Distributor TFI Module(s)? It’s imperative, the Distributor IS the Heat Sink for that Module. So it needs that Compound to Transfer heat to the Distributor- and dissipate it. Or it will cook! There is also a necessity to have a solid Block to Distributor Ground- (Grounds are a BIG issue). Sensors are reverse of common thought. One would think Power would be Switched on Sensors- Ground always Solid. In actuality- the GROUND is what the EEC switches on/off, Power is always present, or generated (Such as 02 Sensors). There’s a few good TFI diagrams, Sensors, Ignition Switch, etc. i’ll post It for you. Actron makes an OBD-1&2 tester in one 30$ +/- Very good to have. Plugs in to the Diagnostic Connector- gives the Code# and the description. The Other option is old school, jumper wire across the correct Diagnostic Connector pins, it will illuminate the Dash Check engine light- it flashes and you visually record the flash counts-it gives you the multi digit Code, you look up the #. Ignition Switch- replace it, I’m still thinking the issue is elsewhere- but if it’s not right- replace it for sure! No loose ends. Go to RockAuto. Com. You will find great prices for quality Parts, there.
If you have Codes in the EEC, you need to read them, then DUMP them. If they’re Codes there- it Can affect the Grounds for certain Sensors, may malfunction. It’s a Grey Connector right on the Drivers side engine compartment- hangs off the Firewall. All you need is a 5$ Test light. A Haynes (Not Owner’s- Technical) Technical Manual is handy, Lots of info to familiarize yourself with things.
If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars. (Yours is NOT this, unless it has the California Emissions Sticker on the Radiator support- you have a CEL (Check Engine Light)that works, note that a CEL light Flashing when Accelerating (About 1.5 second intervals- and stops flashing when not accelerating). If occurs while accelerating this means you have a Cylinder missing. Spark issue. This is the same for an OBD-1 (your 91’ LX) or (82’GT to 1995 GT’s) and OBD-2 (1996-up GT/LX’s). Good info below. I’ll add a few things that are missing, but it’s pretty informative. Take a read...

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89 through 95 cars have a working Check Engine Dash light. Watch it instead of using a test lamp.

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The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10

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Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus Digital Ford Code Reader (3145) Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
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The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. —>If the problem does not occur when the engine is cold,<~~~(?)the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

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See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton
DVOM= Digital Volt/Ohm Meter, a Basic Meter for measuring Ac or Dc Volts, Ohms, some measure Amperage (Limited to a certain amount of Amps), Continuity (Some Audible). 2 leads Red/Black- a Rotary selector in Center to measure what you are seeking. If you’re looking for Ohms (Resistance) select OHMS close to what you are expecting- most are ‘Auto ranging’ meaning if you select a different amount than you need, it will read what’s there. Only thing you want to remember using one is- you are reading DC- rotate the knob so it points to DC, or AC to AC. They are much more forgiving these days- than 10-15yrs ago- no
worries. Look at the Manual. Just ensure that if you buy one that you have to plug leads in to the Meter- plug Red into ‘Voltage’ and Black into ‘Common’ (Usually have lead Colors next to them). The other hole is for measuring Series Amperage, and will SAY “AMPS” next to it- and the Maximum amount of AMPS you can read- I.e. “10 AMPS MAX!!” Read the book if you want to do that, all a little bit different, shouldn’t need to read “Amps”using one on the Car. Only likely DC Volts, or Ohms, or Audible Continuity (like checking a disconnected wire). NEVER have the Plug into the “AMPS” hole, and read Voltage, or Vise versa. Again- they are pretty safe in that area now- but NEVER ASSUME THAT! Plug Red and Black Wires into the 2 Holes like I said, only. You’ll likely never need the other. Questions- ? read the Manual- best bet! Ask the Manager of the Store to show you how to use it. Remember one thing- Measure “Ohms” only on items that are listed- a small amount of current flows into anything you measure Ohms or Resistance on. It won’t hurt you- won’t even feel it- but into a wire/wires or pins going through/into the Computer- or an 02 Sensor- you can possibly damage it. So, just read across what are reliable sources. Which is why I suggested a ‘Shop Manual’. You can find a Service Tech Manual for your Car likely on EBay. A little easier to understand Manual- a Haynes, AutoZone or RockAuto cheaper. A good set of tools to have- A DVOM like this- can get a real simple one for 10-15$, a Test light is a useful tool, and an OBD-1 Meter to read Codes. Tech.Manual on your Car. You need to read verify values, pull Codes- the most simple, accurate way. Then dump them. You may also be able to dump the EEC Codes simply by disconnecting the Battery for 30-45 Minutes- only way it won’t clear them is if it still has the same issue. Gap your Plugs at 0.052-0.056, running Motorcrafts- right? Good luck! Have another diagram- phone’s dying, I’ll get it to you today- tonite.
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diagram courtesy of Tmoss & Stang&2Birds
 

08GT500

Active Member
Jul 12, 2018
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Thanks regarding the GT500, it’s really an experience- like a badass 5.0 that takes off like a bullet- but as my friend said, it unnaturally just doesn’t stop pulling and sticks you hard to the seat (So hard he bitched for an hour about his neck after the ride) and never saw him so nervous when I did a 3 Gear Burnout- no Clutch, and were still
Pulling hard at about 80 and still spinning. Only bad- they don’t like to hook and zigzag- but predictably....and a good- they don’t like to hook and zigzag- but predictably Need another Garage, too many projects backing up. The 89’
S back together...
 

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08GT500

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I really despise replacing GT40P STOCK Springs when the person sticks in an E303 Cam and 1.7 Rockers- giving it .523 Lift vs..498 with 1.6’s- which is too much for the Stock GT40P Springs- alone. Eats Valve Seals, destroys Hydraulic Roller lifters, occasionally snaps the Timing pin in the Cam- lots of force- saved mostly by Pushrods too short, snapped 2 Roller Rocker pins- that’s only going into the lifter only about 0.010 vs a nice 0.030-0.060 with a 3/4 turn of the Allen Head Bolt. Getting a Compressor line into the angled Spark Plug holes is another fun task with those BBK Long Tubes (to hold up the Valves). So much easier to tear the Heads off and do at least a nice port match and Chamber Polish- ensure the Valves get a nice 3 angle valve job. Like Stud mounted Rockers- not a fan of the Pedestals for a modified Motor. This is # 5 this year with the same issue- one Cam had .644 lift, lol! The Rockers pinsc all sheared and were all destroyed- making contact with the retainers..That’s what I meant by “going Overboard”.
 

08GT500

Active Member
Jul 12, 2018
904
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G’morning..make any headway on your LX? Sounds like a nice, solid build, should be a rocket! You happen to use the Heat Sink Compound on the TIF, Solidly grounded Distributor and Code acquisition and Code Dumping- whether done the simpler way- or w/ a paper Clip or battery terminal removal to dump any lingering engine codes in the EEC via the engine bay connector once you acquire any other Codes that the Car has stored. Did you get the flow Data printouts of your Builder for the actual head flow Data? I’m firing that 89’
https://pinterest.com/pin/create/bu...w what all the 2 and 3 digit codes are about.
https://foxstang.com/reading-mustang-trouble-codes-eec/#
The fox Mustang’s EEC IV computer has two connectors for self-testing and located on the driver-side firewall. The large connector contains the self test output (STO) and ground (SIG RTN). The small pigtail is the self test input (STI). You can easily grab your trouble codes, and this will help you diagnose your MIL or “Check engine ” light on that fox body Mustang of yours! Note: Make sure your engine is warmed up before doing these tests.
Counting Digits to Get Your Trouble Codes
If you don’t have a code-scanner, you can count the signals and find the codes that way. It may take patience to do so but doable. To get a code digit: There’s a 2 second pause between digits and 4 second pause between codes. So for code example “21”, you will count two flashes, a 2 second pause, then a single flash, if there’s another code – it will pause 4 seconds.
Using a Test Light (86-88 Mustangs)
The 86 to 88 Mustangs will need a jumper wire from the STI (test input) with the #2 pin on the connector (I’d use spades) and you can hook your light to #4 on the connector and (+) to the positive battery terminal.
test-light-eec-jump-test-trouble-code.png

Using The Check-Engine Light (89-93 Mustangs)
The 89-93 Mustangs (and the 94-95’s as well as some ’88 MAF equipped Mustangs) will allow you to use a jump wire and count the check-engine light in the dash. The jump wire (I’d use spades on each end) would connect the STI (test input) with #2 pin on the connector, see below:

eec-jump-wire-fox.png

Test Conditions and EEC-IV Codes Below:
(O) =Key On Engine Off (KOEO)
(R) =Key On Engine Running (KOER)
(M) =Memory code
(C) = Continuous memory
2 Digit Codes
Code Condition Cause 11O,R,CSystem OK, testing complete12RIdle speed control out of specified range13O,R,CNormal idle not within specified range14O,CIgnition profile pickup erratic15OROM test failure15CPower interrupt to computer memory16RErratic idle, oxygen sensor out of range or throttle not closing17RCurb idle out of specified range18RSPOUT circuit open19ONo power to processor19RErratic idle speed or signal21O,RCoolant temperature out of specified range21O,R,CCoolant temperature sensor out of specified range22O,R,CMAP sensor out of specified range23O,R,CThrottle position signal out of specified range24O,RAir charge temperature low25O,RMass Air Flow sensor or circuit27CVehicle Speed Sensor or circuit280,RVane air temperature sensor or circuit29CNo continuity In Vehicle Speed Sensor circuit31O,R,CCanister or EGR valve control system32O,R,CCanister or EGR valve control system33R,CCanister or EGR valve not operating properly34O,R,CEVP voltage above closed unit35O,R,CEGR pressure feedback, regulator circuit38CIdle control circuit39CAutomatic overdrive circuit41COxygen sensor signal41RLean fuel mixture42R,CFuel mixture rich43CLean fuel mixture at wide open throttle –43REngine too warm for test44RAir management system inoperative45RThermactor air diverler circuit46RThermactor air bypass circuit47RLow flow of unmetered air at idle48RHigh flow of unmetered air at idle49CSPOUT signal defaulted to 1 0-degrees51O,CCoolant temperature sensor out of specified range52O,RPower steering pressure switch out of specified range53O,CThrottle Position Sensor input out of specified range54O,CVane air flow sensor or air charge temperature sensor55RCharging system under specified voltage (1984 through 1988)55ROpen ignition key power circuit (1984 through 1988)56O,R,CMass Air Flow sensor or circuit57CTransmission neutral pressure switch circuit58OCFI – idle control circuit; EFI – vane air flow circuit58RIdle speed control motor or circuit58CVane air temperature sensor or circuit59O,CTransmission throttle pressure switch circuit61O,CCoolant temperature switch out of specified range620Transmission circuit fault63O,CThrottle Position Sensor or circuit64O,CAir Charge Temperature (ACT) sensor65CFuel control system not switching to closed loop66O,CNo Mass Air Flow sensor signal67O,R,CNeutral drive switch or circuit67CAir conditioner clutch switch circuit69O,CVehicle Speed Sensor or circuit72CSystem power circuit, electrical interference72RNo Manifold Absolute Pressure or Mass Air Flow sensor signal fluctuation73O,RThrottle Position Sensor or circuit 2174RBrake on/off ground circuit fault 2175RBrake on/off power circuit fault 2276RNo vane airflow change77RThrottle “goose” test not performed78CPower circuit 179OAir conditioner clutch circuit81OThermactor air circuit82OThermactor air circuit, integrated controller circuit83OEGR control circuit (four-cylinder models oeM83OCooling fan circuit (V6 models only)83O,CLow speed fuel pump relay (1984 through 1988 models)83O,CEGR solenoid or circuit (1989 and later models)84O,REGR control circuit85O,RCanister purge circuit or transmission shift control circuit85CExcessive fuel pressure or flow85CCanister purge circuit86CLow fuel pressure or flow87O,R,CFuel pump circuit D288OIntegrated controller89OLock-up solenoid91R,COxygen sensor problem, fuel pressure out of specified range or injectors out of balance92RFuel mixture rich, fuel pressure high93OThrottle Position Sensor or circuit D94RSecondary air system inoperative95O,CFuel pump circuit problem95RThermactor air diverter circuit96O,CFuel pump circuit96RThermactor air bypass circuit98RRepeat test sequence99RRepeat test sequence99RSystem has not learned to control idle speed 3 Digit Codes (some 91+)
Code Condition Cause 111O,R,CSystem Pass112O,R,CAir Charge Temp (Ad) Sensor circuit below minimum voLtagE/ 254 F113O,CAir Charge Temp (ACT) Sensor circuit above maximum voltagE/ -40 F114O,RAir Charge Temp (ACT) out of self test range116O,RCoolant Temp (ECT) out of self test range117O,RCoolant Temp (EdT) Sensor circuit below minimum voltage/ 254 F118O,CCoolant Temp (EdT) Sensor circuit above maximum voitage/ -40 F121O,CClosed Throttle Voitage higher or lower than expected122O,R,CThrottle Position (TP) Sensor circuit below minimum voltage123O,CThrottle Position (TP) Sensor circuit above maximum voltage124O,CThrottle Position (TP) Sensor voltage higher than expected125CThrottle Position fTP) Sensor voltage lower than expected126CBP Sensor higher or lower than expected129O,R,CInsufficient Mass Air Flow (MAE) change during Dynamic Response Test144CNo Oxygen Sensor (HEGO) Switches detected157CMass Air Flow (MAE) Sensor circuit below minimum voltage158O,CMass Air Flow (MAE) Sensor circuit above maximum voltage159O,RMass Air Flow (MAE) Sensor out of self test range167RInsufficient Throttle Position change during Dynamic Response Test171CFuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch172R,CLack of Oxygen Sensor (HEGO) Switches, indicates lean173R,CLack of Oxygen Sensor (HEGO) Switches, indicates rich179CFuel system at lean adaptive limit at part throttle, system rich181CFuel system at rich adaptive limit at part throttle, system lean182CFuel system at lean adaptive limit at idle, system rich183CFuel system at flch adaptive limit at idle, system lean184CMass Air Flow (MAE) higher than expectec185CMass Air Flow (MAE) lower than expected186CInjector pulse width higher than expected187CInjector pulse width lower than expected211CProfile Ignition Pickup (PIP) circuit fault212CIgnition module circuit failure – SPOUT circuit grounded213RSPOUT circuit214CCylinder Identification (CID) circuit failure215CEEC Processor detected Coil 1 primary circuit failure216CEEC Processor detected Coil 2 primary circuit failure218CLoss of ignition Diagnostic Monitor (1DM) signal-left side222CLoss of Ignition Diagnostic Monitor (1DM) signal-right side223CLoss of Dual Plug Inhibit (DPI) control224CErratic Ignition Diagnostic Monitor (1DM) input to processor225RKnock riot sensed during Dynamic Response Test327O,R,CEVP circuit below minimum voltage328O,R,CEGR “closed valve” voltage lower than expected332R,CInsufflcjent EGR flow detected334O,R,CEGR closed valve voltage higher than expected337O,R,CEVP circuit above maximum voltage341OOctane Adjust Service Pin in use411RCannot control RPM during KOER low rpm check412RCannot control rpm during KOER high rpm check452CIsufflcient input from Vehicle Speed Sensor (VSS)511OEEC Processor Read Only Memory (ROM) test failure512CEEC Processor Keep 4Jive Memory (KAM) test failure519OPower Steering Pressure Switch (PSPS) circuit open521RPower Steering Pressure Switch (PSPS) circuit did not change states522OVehicle not in PARK or NEUTRAL during KOEO528CClutch Switch Circuit failure536R,CBrake On/Off (BOO) circuit failure I not actuated during KOER538RIsuffIcient RPM change during KOER Dynamic Response Test539OAC On/Defrost ON during KOEO542O,CFuel Pump secondary circuit failure543O,CFuel Pump secondary circuit failure556O,CFuel Pump Relay primary circuit failure558OEGR Vacuum Regulator (EVR) circuit failure5640ElectrOD FAN( EDF) circuit failure565OCanister Purge (CANP) circuit failure566O3-4 Shift Solenoid circuit failure629OConverter Clutch Control circuit failure998O,RHard Fault present


Kind of a bonus test that tells you the health of the Cylinders- if you choose to. Once your KOER test is complete (after all the stored trouble codes cycle four times) you can initiate a cylinder balance test. Activate the test by quickly tapping the throttle. The idle will rise and fall a bit, but don’t worry because it’s just the good old EEC-IV doing its job. The codes will appear in a different format from all the previous tests because the flashes now hold a value of 10. Each flash is worth 10, so if the Check Engine light flashes seven times, this would mean code 70, which means that cylinder No. 7 has failed the test. This could be due to an ignition problem or a compression leak. While the code won’t pinpoint the actual cause, it will get you in the ballpark and show you where to look. One to eight flashes correspond to their respective cylinder.
Clearing the codes Some stay away from clearing the codes unless you’ve already fixed all the trouble codes you initially had. Since the EEC-IV is an early version of the “adaptive strategy”
OBD-2 Computer used now, has to relearn a few certain things- won’t make it run bad- mostly driving habits it’s learning- and does this on its own. You can READ Codes without clearing if you want, but it CAN have an effect on some of the Sensors as the same Grounds is used on some Sensors if lingering Codes remain present. Try without clearing the first time if you want- if you nailed the issue- or confirmed it, and repaired, runs fine- skip the dump if you like-I prefer to read and then eradicate them.
Procedure: You can do this by is simply disconnecting the battery for a short period, as said before. This will trigger code 15; this means that the Keep Alive Memory (KAM) test failed. This is done so you don’t cheat the sniffer test by clearing trouble codes whenever you want. Every time the codes are cleared, the ECU will have to relearn its driving pattern by completing a full drive cycle where every potential driving situation is simulated, takes a few Drive cycles to “relearn”. To clear code 15, you will need to perform a KOEO self-test. Once you turn the ignition switch on and the codes start to flash, you’ll have to disconnect the Self Test Input (STI) jumper wire. Once you’ve done that you can turn the ignition off and then run another KOEO self-test to make sure that code 15 is no longer present in the Continuous Memory code. Good luck!!
 

PakstinN

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well, yesterday I took her out for a drive to the parts store to try and get an eec-iv tester, got to the parts store (they didn't have the tester) and when I tried to leave, the car wouldn't start..went inside and picked up a cheap multimeter and started checking out the fuel system (fuel pump wouldn't prime) found out we have 12 volts running clear back to the pump yet the pump still seems to have inconsistent power..ended up pulling the fuel tank off in the advanced autocrats parking lot and finding out that the positive wire running from the connector to the fuel pump was SEVERELY corroded and and was making intermittent connection..that combined with the faulty ignition switch I believe could be a lot of my gremlins I have been dealing with lately. anyways, I am going to order a new fuel pump bracket and fix that the correct way, I also replaced that switch while we were working on the car yesterday...so hopefully when I get to putting this thing back together, she once again runs and drives like I know she can. I cannot thank you enough for all the information you have given me though, I think I may also try and track down that obd1 code tester and pull codes that way after I replace the parts I know are bad. either way, that is good information to have and I will certainly put it to good use!
 
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08GT500

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Jul 12, 2018
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Awesome!!!! Problems revolve around something newer that settles in, touched, moved, etc..PERFECT example, MOST are not Serious, w/random prob’s- type you see most-Wires/connections. Stores stock OBD-2 stuff, less OBD-1 testers, My Actron does both OBD-1&2 CPU’s is on Amazon- I’ll show you a pic..would show an intermittent lean condition within the System- via 02’s. Motor hitting 6,000rpm- not a Spark integrity issue, yet a loose Coil Wire could mimic it- answer is 99% the simplest one, recently changed items.
The Air/Fuel % gauges I’d mentioned watch/log that, too. I’m very happy (as I’m positive YOU are, lol!) you kept trying, were vigilant. As lean condition can cause engine damage fast at high RPM’s- a “Eureka moment”!. May want to view the plugs and clean-regap-ensure all is OK from the Heat.
Peeps buy Fuel pressure gauges- say “But I have good fuel pressure”- and they may- but gauge is #1) Invisible,#2) NOT measuring BOTH consistent FLOW, only PRESSURE. You did excellent, refused to give up- it’d surprise you how many call it quits- sell off, Buyer looks at necessary basics-fixes. Seller is LIVID!!
You have things like the MAP you need to finish, Acquire some Test Items- but you were wrong about One thing. You ARE GOOD at these things, and you’ll get BETTER, just keep on learning- and you’ll excell! I’m always happy to help, all in this together, lol!
My Wife is Building her first Motor, from Scratch, a 70’ 454 CID Stroker 496. She’s got my Micrometer, Telescoping gauges, Plastigauge & She’s Setting up her Crank Bearing Clearances today. I’d taught her to TIG Weld 6061 Aluminum- Miter tube- Chassis Mod’s- a 67’ Nova. Daughter- started her at 5yrs old- drives a 72’ ChevelleSS 396, 4 speed. Built it herself, too. I Dprayed it Electric Blue. But mostly her Work. I LOVE it when Women are engaged in this, way it SHOULD be, Hell damn YES! Thanks, Bro- talk soon!
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08GT500

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Jul 12, 2018
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Top Pic Actron is the OBD-1&2 Scanner, Leads come with- in second Pic. My Autel MaxiDas is Obd-2, does everything from Hyundai’s to Lamborghini’s, need it for doing the newest Cars- create’s Fob’s, every connector for each Mfg., I can change Parameters- even Timing, Fuel Maps, Relerans, connect to the DMV.
That Actron is excellent for most everything, will take Codes pulled- tell what the top fixes for Millions of Dealers were found to be with information it has, live data, freezeframe, replay- and NOT expensive!
 

PakstinN

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Jul 17, 2014
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alright, so I got the car put back together last night (in the rain) and I definitely have the fuel pump issue sorted out, she primes and starts like a dream every time I turn the key. anyways, I took her out for a test drive and have the SAME ISSUE as before. anything above 4000 rpm and over 3/4 throttle and there is a miss. this time I pulled codes..never got a code 11..I believe this to be due to the fact I have that sct 4 bank chip and forgot to turn it back to 0..the other codes I got were 15,55, and 85..also checked ups voltage..voltage varied from roughly .96 at idle to 4.6 at wot...what would you recommend I do next? also, thanks for all the kind words. im only 19 so I realize I have a long ways to go before I am as competent with these cars as most of the guys on this site, but I learn something new almost everyday lol
 

08GT500

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Jul 12, 2018
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Hi Bro. May sound like an unusual comment- but it rings true- Cars seem to Test US, more than US- THEM.lol! Don’t get frazzled- this is typical, you’ve successfully identified and repaired one of your poly issue group. I’m on the Lake today, popped in to check on the very issue present. I’ll get more detailed a little later- SOME IDIOT FORGOT to grab his Wife’s Phone (thought I...) brought one 20% Charged IPhone, no Charge cord —> Me!<—...dumdum..
Hi there! It’s OK, happens like this frequently. One action affects another.Pull your Plugs-Inspect, Clean w/Spray Solvent -Regap. Apply Never Seize to the plug threads, sparingly. Spark plug wires- be SURE they are good, have an Old set? Try if so, use Plug connection grease inside the Wires on Plug Boots and Cap Connectors. Replace if ANY wear is seen. Pull that MAF sensor and Clean (Spray, or fill up Cap with Spray- Soak it for a few- reinstall). Use a Light Solvent (CRC or equivalent). I use Brakleen (non flammable) and PB Blaster are adequate for most every Situation. MAF Sensors I use CRC MAF Cleaner- guaranteed zero residue. Your Vapor Canister Solenoid is not working/Broken (Code 85). Car ever reek of raw Fuel? Exhaust at idle reek, or hitting the Gas- parked- any Black Smoke? Or burns eyeballs out when one smells exhaust under a driveway rev?An 02 Sensor Test is next- and EGR Test, is it all still installed and connected? EGR Can get stuck. If EGR is removed/blocked off- should be within the BAMA Programs, too.
Have you tried a full throttle pull- to 6K with engine Cold, vs @ operating Temp- yet..does that affect the Miss? Simple fix if so. The CPU showed an issue- (15) it’s a CPU “relearning” Code, can also be 2 other things- Check Block Ground to Chassis, Distributor, CPU Ground- ALL Grounds- check Connectors you may suspect- remove, Clean, apply anticorrosive- verify Continuity with your VOM. Get a New Filter yet?. PCV Valve replaced-correct? I’ll walk you through some real-time Tests to fix this if these basics don’t nail it.
If Filter’s a K&N, or similar- check, most Conical types you cannot just clean w/Solvent- even liquid Soap & Water. Well rinsed, (Re-oil.!Do that step after further testing). Verify Filter by Part #, another online listing. Sun dry or use a Hair dryer to speed up Drying..—> Do pulls between each Step or 2 so you don’t not know what helped<——-. Should be able to see the Sun through the Clean/dry Air Cleaner, barely- looking inside and outward through element. Coil input Connections (12V Side)- Check- Clean w/a wire brush- use Noalox or another anticorrosive on all connections you’ve cleaned- tightened. You did use Heat Sink Compound on the TFI- yes? Those are notorious for being bad, even a few in a row- brand new. Just keep in mind.
Having a spare Distributor from a Junkyard Vehicle is a VERY good thing to have, if Motor was ok- vehicle Crashed, etc.. Clean out your internal distributor with the CRC Solvent, should Dry very quick.
Will the Motor Rev-Car sitting, not under load-floored quick to 6,000? I’ll ask if you’d like to speak over the phone later- easier to talk than text, Number’s 4133458331, if you’re uncomfortable with that- we can still text. No worries!
None of this is in vain. You need to verify Solidity in each and every area- this might be a pain- but you will learn more than one could ever just “TELL” you- if you get my meaning. So, Do each test, methodically-one by one and document. Pictures, document in a notebook. Keep Reciepts.
You’re TPS Voltage is OK- but they are like a Potentiometer or like an older stereo’s rotary Volume Switch, they get old, and you hear “crackling” there may be great Voltage idle to wot, but a spot somewhere where the connection is weak or lost at a certain point, intermittently, will cause issues, too-from normal wear.
The 2 large, radial connectors that are coined as “salt n pepper plugs” you will find in your Center- passenger area near the Firewall. Pop them open- Check them for Corroded terminals and clean, sparingly use contact/dielectric Grease once clean(if you have it) not absolutely necessary. Clean, tight, dry Connections are. (NOT the antioxidant, excess can cause “bridging” of connectors.
I keep thinking of the issue starting when the Car was on a Jack, or a Lift? Something maybe affected, pulled on a Vacuum line- it split, Wire on a header, like an 02 line melted to the exhaust System, etc. Be sure you have no Vacuum leak from the Canister vacuum line(s)- and take a peek to see if the Connectors are on Solid. There IS a problem there.
I’ll work with you until this is as it should be, and if you have upgrade questions afterwards. Honestly, there really isn’t a lot that these need to keep running like a freight Train, it’s the Smaller things, mostly. They need not monumental things, but basics done SOLIDLY. Newly implanted engines are a big cause of oddities as lines and wires start to settle in to a new environment, may have been just getting by before- but a little more Heat, stress, etc.can cause mayhem. I promise you will laugh at this once it’s back again, as should be.
I’ll text u later, if you want to talk- Call me around 9-9:30- if that works.(?) You got this- you’re doing GREAT! I’ll Talk to you soon! As always-Good luck!! John
 

08GT500

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Jul 12, 2018
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A good write up regarding TPS adjusting by JR. Check out a site named Xenocron Tuning if you get a minute, started it- left to start my singular Business.(Conflicts of interest, lol). Lots of good Parts and Tuning intros there- as well as free BIN. Files and free Software- burn your own Chips, learn how to Tune- was made to be as a Public Domain spot, where all could learn and not get ripped off. These Sensors also get dirty and can cause incorrect messages to the CPU. Cheers!!


Setting the TPS: you'll need a good Digital Voltmeter (DVM) to do the job. Set the TPS voltage at .5- 1.1 range. Because of the variables involved with the tolerances of both computer and DVM, I would shoot for somewhere between .6 and 1.0 volts. Unless you have a Fluke or other high grade DVM, the second digit past the decimal point on cheap DVM’s is probably fantasy. Since the computer zeros out the TPS voltage every time it powers up, playing with the settings isn't an effective aid to performance or drivability. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.


Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

TPS troubleshooting steps:
1.) Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
2.) Use the Dark Green/lt green & Black/white wires to set the TPS base voltage. Try this... All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a voltmeter with a 1 or 3 volt low scale to do the job.

The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS. Use a pair of safety pins to probe the TPS connector from the rear of the connector. You may find it a little difficult to make a good connection, but keep trying. Put the safety pins in the Dark Green/Lt green wire and Black/White wire. Make sure the ignition switch is in the Run position but the engine isn't running. Set the voltmeter on the 2 volt range if it doesn’t auto range.

Here’s a TPS tip well put from NoGo50

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks.

(copied from MustangMax, Glendale AZ)

A.) Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

B.) When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

C.) Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

D.) The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.

The TPS is a variable resistor, must like the volume control knob on a cheap radio. We have all heard them crackle and pop when the volume is adjusted. The TPS sensor has the same problem: wear on the resistor element makes places that create electrical noise. This electrical noise confuses the computer, because it expects to see a smooth increase or decrease as the throttle is opened or closed.

TPS testing: most of the time a failed TPS will set code 23 or 63, but not always. Use either an analog meter or a DVM with an analog bar graph and connect the leads as instructed above. Turn the ignition switch to the Run position, but do not start the engine. Note the voltage with the throttle closed. Slowly open the throttle and watch the voltage increase smoothly, slowly close the throttle and watch the voltage decrease smoothly. If the voltage jumps around and isn’t smooth, the TPS has some worn places in the resistor element. When the throttle is closed, make sure that the voltage is the same as what it was when you started. If it varies more than 10%, the TPS is suspect of being worn in the idle range of its travel.

TPS will not go below 1 volt

Note: Make all resistance checks with the ignition switch in the OFF position. Failure to do so will result in incorrect results and may possibly damage the meter.

Engine mounted sensor circuit: Check the resistance between the black/white wire on the TPS and battery ground. It should be less than 1 ohm. Higher resistance than 1 ohm indicates a problem with the 10 pin connector, computer or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the black/white wire.

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See the graphic for the location of the 10 pin connectors:
Diagram courtesy of Tmoss & Stang&2birds


TPS_IAB_Pic.jpg



See the graphic for the 10 pin connector circuit layout.
 

08GT500

Active Member
Jul 12, 2018
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Part 2/2 of prepost info on TPS’s. Think I have another Bass hooked!!!

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Unplug the white 10 pin connector to do some resistance testing. It is good time to clean the connector pins and examine the connector for corrosion, broken wire or other damage. See http://oldfuelinjection.com/?p=85 for help in this department.

If the resistance on the TPS Black/White wire and pin 1 of the white engine fuel injector harness 10 pin connector, is more than 1.0 ohm, you have bad connection or broken wiring. Repeat the test using the pin 1 of the white body side 10 pin connector and battery ground. You should have less that 1 ohm. More than that is a damaged signal ground inside the computer or bad connections or wiring.[/b]