Another Frankenstang

ARBOC39

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Sep 19, 2016
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#1
93 4 cylinder body
90 v8
91 interior

Just put this car in garage last night. The MAF and TPS I noticed are already unplugged. Rough idle, not a lot of power, but runs ok. The ECM goes with the motor but the wire harness' are a 93 LX.

Are these harnesses compatible? I found the TPS connector sitting on the valve cover, the MAF connector is nowhere in sight, is it there from the v4 engine?
 
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Mustang5L5

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Feb 18, 2001
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#2
Pull the computer and get the code. Will help figure things out. At this point, we need more info.

They would have had to use a v8 engine harness, and unless they used a 87-88 harness, there should be a MAF connector somewhere


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hoopty5.0

mechanicus terribilis
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#3
The O2 harnesses are year specific, but if it all came from the same car, you shouldn't have any issues.
 

ARBOC39

Advanced Member
Sep 19, 2016
191
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#4
Pull the computer and get the code. Will help figure things out. At this point, we need more info.

They would have had to use a v8 engine harness, and unless they used a 87-88 harness, there should be a MAF connector somewhere


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The chassis is supposed be a 93 4cylinder. The motor is a 90 and was supposed to have had all the wiring harness go with it. If that is true they put it back factory looking along and through firewall, behind glove box looks untouched, or was done really well. It's possible I misunderstood the guy, the front end could be the donor car and the chassis is the original 90 5.0. The title says it's a 4cylinder though. I just starting tinkering, figuring what's what.
The O2 harnesses are year specific, but if it all came from the same car, you shouldn't have any issues.
Colors were hard to distinguish, but a was under fluorescents and a little buzzed last night. I do more digging.
 

ARBOC39

Advanced Member
Sep 19, 2016
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#5
Everyone's pictures of their projects look awesome, I don't know if I could go years without driving it. I won't drive it winter, it's rust free. I or we won't do more than we can handle in a weekend but still want to drive it. I don't think I could handle seeing a completely disassembled car in my garage (again), I'd be depressed knowing it's 5.0 sitting there undrivable. I did derust my 02 F150 and 07 F350, but they are trucks. I.would absolutely love to drive a brand newish cobra out of the garage, that's just not possible, work too much. I'm not looking for a show car, just one that looks driven and babied. It will be done right, my buddies won't allow it any other way. First is just to get everything working correctly before starting anything. I have a feeling the electrical is going to be the biggest headache, but so far so good.
 

Mustang5L5

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#6
The 4 cyl body harness in 1993 would be compatible with the 1990-1993 V8 engine harness. Basically what they probably did was rip out the 4cyl engine harness, and swap in the V8 engine harness. But it would connect to the main interior harness, and body harness of the 4cyl car. For instance, the 4cy harness will have the fog light plugs dangling for the V8 GT car.

What you need to do is identify the harnesses you have, and how the 4cy conversion was done. Mixing and matching harnesses can lead to problems, so you really need to do your homework here.

First thing to do is find out the ECM type, and if the 4cyl was originally a 5-spd, or automatic car. Is the car now a 5-spd or auto? Does the computer match the transmission, and o2 sensor harness?
 

ARBOC39

Advanced Member
Sep 19, 2016
191
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Massachusetts
#7
Waiting on new code reader, thanks 5L5. Asked the Google genie about the surging idle .35v on TPS, no matter how I spun it would not go above .55, the idle took off crazy, so I just left it unplugged for now, new one on way. On to the pcv, is that grommet supposed to fit tight? Oil everywhere, if car was upside down the pcv fitting would have just fallen out. I hope that's not normal, held in by vacuum or something, new valve on way also. Took the hood off, wow! So much easier, now I need better lights in garage. Still can't find maf connector, it's definitely a 93 LX 2.3L wire harness attached to a 90 v8 engine harness. I get these sensors working the computer just readjusts itself I hope? Changed oil, black sludge. BASTARDS! Tomorrow another day.
 

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Mustang5L5

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#8
Given the info from your PM, you are running an 87/88 speed density 5spd computer. I bet the engine harness matches too meaning it doesn't have the provision for mass air. Definitely a Frankenstang.

Now, given your comment about the TPS voltage being off, you might have a wiring problem. When you test the other wire in the TPS, do you get 5 volts?

If not, then I think you've love your Vref 5 volts that powers the main sensors. This usually happens when there is a wiring issue.


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ARBOC39

Advanced Member
Sep 19, 2016
191
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#9
Given the info from your PM, you are running an 87/88 speed density 5spd computer. I bet the engine harness matches too meaning it doesn't have the provision for mass air. Definitely a Frankenstang.

Now, given your comment about the TPS voltage being off, you might have a wiring problem. When you test the other wire in the TPS, do you get 5 volts?

If not, then I think you've love your Vref 5 volts that powers the main sensors. This usually happens when there is a wiring issue.


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Does car need to be running to check voltage? Kids sleeping (glasspacks). I looked everywhere, can't even find wire colors at firewall, so you're right about map. The TPS was disconnected so long the holes are plugged and green and very small. Male is no better but has pins to clean. Splice to egr is exposed, solder intact but a lot of strands not spliced. Will I get normal voltage before the fault or is.it constant low voltage back to ecm? How often do wires go bad in the harness? Is it usually at a connector or test pinhole?

Original car had a/c, engine doesn't have compressor, can that be added on?
 

Mustang5L5

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#10
No, you just need to turn the key to ON to check for voltage. A lot of the sensors use 5V power and then send back their signals to the ECM. Sometimes what happens is that when harnesses get mixed and matched, voltage gets sent back on the wrong wire and you fry a trace in the ECM and have bad voltage to the sensors. Would explain why it's running like crap.

You've gonna need some wiring diagrams If the TPS doesn't have it's 5V reference voltage.

Yes, AC can be added. The plug for the compressor is located near the coil, and usually theres a 2 foot wire that plugs into here and into the compressor that you may need to locate.

If you find you are missing the voltage, I think you are going to have to track down a 92-93 V8 Mustang 5-spd engine and o2 harness and swap that in, along with a Mass Air 5-spd computer. Probably $400-500 in parts for all that. But before that, lets confirm you have a hack job mess under the hood.
 

ARBOC39

Advanced Member
Sep 19, 2016
191
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Massachusetts
#11
I get 5.14v, .11v, .11v on the three wires at connector, TPS disconnected.

Took clutch cable out last night. Taped funnel of oil to one end, it all drained through over night. No change. Clutch does a slip/stick in 1/4" increments to create a vibrating sticking sensation. This is at all times, engine off or running.

Side note, bought car from 18 year old kid, all 4 tires are bald. I've asked three different times about clutch, keeps dodging question.
 

ARBOC39

Advanced Member
Sep 19, 2016
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#12
Maybe I'm cheating. Left TPS disconnected and adjusted idle to 900 rpm or so, is that a bad idea? Idles damn near perfect now.

Engine codes 10, 43, 63, 67, 81, 82 wtf
 

ARBOC39

Advanced Member
Sep 19, 2016
191
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Massachusetts
#13
Maybe I'm cheating. Left TPS disconnected and adjusted idle to 900 rpm or so, is that a bad idea? Idles damn near perfect now.

Engine codes 10, 43, 63, 67, 81, 82 wtf
Ok, I know it wasn't right. Hooked TPS back up and sat there and adjusted it until I finally got to 1.087v, a c hair past that it drops to .445, if not lower. I tightened screws at 1.087 and ran smoothly at about 1100/1200 rpm, adjusted idle screw back, didn't go down. Then the engine vibration changed the voltage back to .445 and it stalled. The sensor is pretty beat up inside, plastic mashed. I think it's works internally, but is just too caddywampass to stay constant. New one on way. My buddy finally stopped over, he thinks it's cable warn out causing sticking clutch. Tomorrow another day, Pats on.
 

Mustang5L5

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#14
Don't spend too much time chasing TPS voltage or how well it runs at what voltage. As soon as the engine shuts off, it's all reset.

Every time you cycle the key to on, the eec looks at the voltage and sets that as idle reference voltage. So as throttle advances, timing changes. That's why twisting the TPS generates a response. The car thinks you are feeding in throttle and the response is simply change in timing. As soon as you shut the car off, it's all forgotten.

All you need to do is make sure TPS voltage at idle is between 0.6 and 1.1 volt. If it's between that, leave it alone. There's nothing to adjust


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Mustang5L5

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#15
Oh, to set idle. Unplug the idle air controller, twist in the throttle stop screws a few turns and start the engine. Now back down the idle stop screw to as low as you can go and have the engine idle smoothly.

When you get it to where you want, check TPS and make sure between 0.6 and 1.1 volt. Adjust only of outside that range.

Once set, shut car off, plug IAC back in, and disconnect battery for 30 mins.

Reconnect battery and start engine. Let idle 2 mins, then turn on every power accessory and ac (if it works) and let run 2 more mins. Shoul start to idle better.

Once running ok...run codes again


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ARBOC39

Advanced Member
Sep 19, 2016
191
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#16
Oh, to set idle. Unplug the idle air controller, twist in the throttle stop screws a few turns and start the engine. Now back down the idle stop screw to as low as you can go and have the engine idle smoothly.

When you get it to where you want, check TPS and make sure between 0.6 and 1.1 volt. Adjust only of outside that range.

Once set, shut car off, plug IAC back in, and disconnect battery for 30 mins.

Reconnect battery and start engine. Let idle 2 mins, then turn on every power accessory and ac (if it works) and let run 2 more mins. Shoul start to idle better.

Once running ok...run codes again


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Idle air controller, is that the same as idle air bypass? The connector on side of throttle body?
 

ARBOC39

Advanced Member
Sep 19, 2016
191
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Massachusetts
#17
Maybe I'm cheating. Left TPS disconnected and adjusted idle to 900 rpm or so, is that a bad idea? Idles damn near perfect now.

Engine codes 10, 43, 63, 67, 81, 82 wtf
81 82 were the tad and tab, rusted or rotted away. They're the 93 ones spliced in, had to order connectors for 90 v8 that was cut out. Replacing egr solenoid also.

Code 43 is o2 sensor, would the other problems cause this code? Once all the parts are in I'll clear codes and start over.

Vacuum line to fuel tank is cut and capped, should that go back?
 

Mustang5L5

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#18
Idle air controller, is that the same as idle air bypass? The connector on side of throttle body?
Yes, same thing. Bolted on the side of the TB. Adjust your idle with that disconnected. If engine stalls out, open the idle set screw more until the engine runs, then lower it down to the lowest stable idle you can get, or feel comfortable with.

The idea is that the idle air controller controls the idle through the computer. If you adjust idle with the screw with it connected, the computer will try to lower or raise isle.
 

Mustang5L5

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#19
81 82 were the tad and tab, rusted or rotted away. They're the 93 ones spliced in, had to order connectors for 90 v8 that was cut out. Replacing egr solenoid also.

Code 43 is o2 sensor, would the other problems cause this code? Once all the parts are in I'll clear codes and start over.

Vacuum line to fuel tank is cut and capped, should that go back?

If you want to see if it's the O2 sensors, swap the two sensors to other sides and see if the codes changes. If it does, buy a new sensor. Vacuum leaks can also cause the code, or a big exhaust leak as well.

As for vac line to the fuel tank, is your charcoal canister there?
 

jrichker

StangNet's favorite TOOL
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#20
81 82 were the tad and tab, rusted or rotted away. They're the 93 ones spliced in, had to order connectors for 90 v8 that was cut out. Replacing egr solenoid also.

Code 43 is o2 sensor, would the other problems cause this code? Once all the parts are in I'll clear codes and start over.

Vacuum line to fuel tank is cut and capped, should that go back?
Code 41 or 91. Or 43 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

Revised 11-Jan-2015 to add check for fuel pressure out of range

Code 41 is the passenger side sensor, as viewed from the driver's seat.
Code 91 is the driver side sensor, as viewed from the driver's seat.

Code 172 is the passenger side sensor as viewed from the driver's seat.
Code 176 is the driver side sensor, as viewed from the driver's seat.

Code 43 is not side specific according to the Probst Ford Fuel injection book.

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors 87-93 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear.

Disconnect the O2 sensor from the harness and use the body side O2 sensor harness as the starting point for testing. Do not measure the resistance of the O2 sensor , you may damage it. Resistance measurements for the O2 sensor harness are made with one meter lead on the O2 sensor harness and the other meter lead on the computer wire or pin for the O2 sensor.

Backside view of the computer wiring connector:
a9x-series-computer-connector-wire-side-view-gif.71316.gif


87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
The computer pins are 29 (L\RH O2 with a dark green/pink wire) and 43 (LH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor
The computer pins are 29 (LH O2 with a Gray/Lt blue wire) and 43 (RH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Testing the O2 sensors 94-95 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 29

91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 29

94-95 5.0 Mustangs:
Computer pin 29 Red/Black – LH O2 sensor
Computer pin 27 Gray/Lt blue – RH O2 sensor
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 27

There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged and the contacts are clean and not coated with oil.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Check the fuel pressure – the fuel pressure is 37-41 PSI with the vacuum disconnected and the engine idling. Fuel pressure out of range can cause the 41 & 91 codes together. It will not cause a single code, only both codes together.

Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

Code 41 can also be due to carbon plugging the driver’s side Thermactor air crossover tube on the back of the engine. The tube fills up with carbon and does not pass air to the driver’s side head ports. This puts an excess amount of air in the passenger side exhaust and can set the code 41. Remove the tube and clean it out so that both sides get good airflow: this may be more difficult than it sounds. You need something like a mini rotor-rooter to do the job because of the curves in the tube. Something like the outer spiral jacket of a flexible push-pull cable may be the thing that does the trick.

If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.




Code 67 –
Revised 2 Nov 2012 to add definition of the NSS functions for both 5 speed and auto transmissions

Cause of problem:
clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests.

External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.

What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

The following is for 5 speed cars only.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!




Code 63 - Throttle Position Sensor (TPS) signal too low.

Revised 02-Jul-2009 to update TPS setting procedure & add 10 pin connector layout.

Vref missing (5 volt reference voltage supplied by the computer), bad connections or damaged wiring, TPS sensor failed, TPS sensor way out of adjustment. Use a DVM to check for 5 volts on the Orange wire. If it is missing, look for +5 volts at the Orange wire on the EGR or MAP/Baro sensor located on the firewall near the center of the car. If there is +5 volts on the MAP/Baro sensor, but not on the EGR, clean the #2 & #5 pin on the white 10 pin connector. If there is +5 volts on the EGR but not on the TPS, look for bad wiring inside the engine fuel injector harness.

See the graphic for the 10 pin connector circuit layout.


Setting the TPS voltage
You'll need a Digital Voltmeter (DVM) to do the job.

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

Always use the Dark Green/lt green & Black/white wires to set the TPS base voltage.

Do the test with the ignition switch in the Run position without the engine running.

Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
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.

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.

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.

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.

The TPS is a variable resistor, much 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.[/b]
 
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