Won't exceed 2500 rpm in any gear, (bogging) when warmed up

C

crisharrison77

New Member
Mar 25, 2011
15
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Palm City
#1
I have a 91 LX 5.0. I put a cold air intake on it, after a while, the car would (SOMETIMES) bog at the lower rpm pf each gear, but would pull through it just fine, (mostly happened with first use of the car during the day, or after sitting a while during the day). Since then, I increased the timing to 15, replaced spark plugs. Has had a slow to start issue here and there. 2 days ago, it was doing a slow to start deal, and it smoked the thin black wire to the negative post on the battery. Next turn of the key it cranks right up. I immediately took the battery back to the place I bought it (under warranty). With a brand new battery, car cranks up just fine. Revs up just fine. Put it in gear, try to take off, and it bogs down. then it cleared up. Made it home just fine. I have a 35 minute drive to work. Yesterday morning driving to work, about 20 minutes into the drive, and cruising at about 77mph, the cars just falls off in power (bogs down), and will not exceed 2500 rpm, regardless of what gear I'm in. I find a broken vacuum line, and fix that. Take it for a quick spin, feel nothing wrong. During the drive home, same thing happens as in the morning. Yesterday afternoon, I replace the Ignition coil, and the fuel filter, take the car for a nice HARD 30 minute run, and no issues. this morning coming to work. Same thing happens, 20 minutes into the drive, just bogs down and wont go over 2500 rpm.

Any leads as to what may be causing this issue?
 

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#2
That thin black wire going to the negative cable is the computer ground wire, if that wire is smoking you have a bad connection, check the wire itself, also that black connector on that wire i would remove and go with straight wire and make sure the eyelet is shiny clean and the fender where it bolts or screws to is shiny metal clean.
 
#3
Sounds like the PIP module in the distributor to me, I went nuts one summer chasing that thing down. Ran fine till like 15 mins of driving and would not rev past 2500 like that, it was like a rev limiter when it hit it. I would also do the TFI just to be safe
 
#4
The thin black wire:
only the one time did smoke come from the hood, and hasn't happened since the battery was replaced. She starts GREAT now.

The PIP module and TFI ignition module:
It was recommended to me today at work to try changing the Ignition module(TFI)

The PIP Module, is that the Pick up coil in the distributor?
 
#5
The thin black wire:
only the one time did smoke come from the hood, and hasn't happened since the battery was replaced. She starts GREAT now.

The PIP module and TFI ignition module:
It was recommended to me today at work to try changing the Ignition module(TFI)

The PIP Module, is that the Pick up coil in the distributor?
 
#6
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it.

To remove the gear, first you drive out the roll pin that secures the gear to the shaft. Then you get to press the gear off with a hydraulic press or puller. When you go to press the gear back on, it has to be perfectly lined up with the hole in the gear and shaft. I have been told that the hole for the pin is offset slightly from center and may require some extra examination to get it lined up correctly.

Most guys just end up replacing the distributor with a remanufactured unit for about $75 exchange


PIP problems & diagnostic info
Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.
 
#7
my car had the same problem a few months ago. it turned out to be either the MAF sensor or the TPS sensor. i replaced them both at the same time, so im not sure which one was the culprit. definately check those two things out if the ground wire doesnt fix the problem.
 
#8
Here's a little more info about the car after having trying to fix it the last couple days, and see what kind of help I can get afrom everyone.

It has a cold air intake.
Items replaced:

Spark Plugs (Gap 45)
Fuel Filter
Ignition Coil
(Test Drive)
Ignition Module (TFI Sensor)
(Test Drive)
Distributor (which of course came with a new PIP Sensor)
(Test Drive)
New plug wires
(Test Drive)

What I have found out during and after the test drives are this. The missing/bucking/bogging does ALSO happen with NO LOAD on the motor ar 2000-2500 rpm. Also the aft spark plug 4 & 8 (ONLY) have un-burnt fuel residue on the threads (But clean tips), of course running very rich, as a co worker of mine said he could smell me before he saw me when driving to work Friday morning (of course this was during the bogging time)

I do not have a code reader yet, and am possibly looking to purchase one tomorrow.

Any suggestions or help would be greatly appreciated.

Thanks
 
#9
Save your money and don't buy a code reader. all you need is a 2 cent paper clip.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 18-Mar-2011 to advise differences in code information for engine running and engine off codes.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

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 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.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

Underhoodpictures007-01.jpg


Underhoodpictures010.jpg


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.

attachment.php


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.

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

attachment.php


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.

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.

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

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) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
 
#10
KOEO Code

96
Fuel Pump secondary circuit failure (Batt to ECA) OR High Speed fuel pump circuit open



KOER

94
Thermactic air system INOP (Left side)

44
Thermactic air system INOP (Right side)

(I do NOT have a smog pump installed and the two hard lines off the back of the block has a hose running one hard line back to the other)
 
#11
Also only seems to do it when driving at speeds of 80 or greater when the problem kicks in. The problem then will continue till the car is turned off and just sits for just a minute or two. Then it will drive fine, under 80 mph. I mean I got it back up to 60 for an extended period of time with no issues, even stopping for lights after the long run. But get on the interstate and drive at 80 or more for less than 5 miles and the problem kicks in.

I also replaced the fuel pump relay, and didn't fix it.
 
#12
Code 96 causes & tests 91-93 models. – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump circuit lost power at one time or another.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier model cars is under the passenger seat. On Mass Air Conversions, the signal lead that tells the computer that the fuel pump has power may not have been wired correctly. See Mustang Mass Air Conversion | StangNet

Diagram of the fuel pump wiring for 91-93 cars.
attachment.php


Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. No voltage when jumpered, check the fuel pump relay and fuse links.
attachment.php


Power feed: Look for 12 volts at the pink/black wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, or connections. Remember that on 92 or later models the fuel pump relay is located under the Mass Air meter. Watch out for the WOT A/C control relay on these cars, as it is located in the same place and can easily be mistaken for the fuel pump relay.

Relay: Turn on the key and jumper the ECC test connector as previously described. Look for 12 volts at the dark green\yellow wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.

attachment.php


91-93 Models:
Using the diagram, check the dark green/yellow wire from the fuel pump relay: you should see 12 volts or so. If not the relay has failed or is intermittent. Check the inertia switch: on a hatch it is on the drivers side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Pink/black wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the dark green/yellow wire, swap the relay.


Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

Revised 28-Oct-2009 to correct code definitions and operation.

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
 
#13
Havent been able to do anything trouble shooting wise to the car in the last couple days but thought I'd share this mornings happenings.

So on the drive to work today I figured I'd try something different to maybe help in troubleshooting. My mustang is a manual shift, The last stretch of road before work I decided id push it up over 80 and see if it would do it again, (cause I've driven the car the past couple days but not exceeding 75), and of course it did bog down. WHILE STILL DRIVING ON THE ROAD. I put the car in neutral and shut the car off, and immediately cranked it back up. Just like the initial cranking of any day, at any time, any temp, the car bogged for just a minute and then it was gone (as long as you didn't get over 80 again).

Just food for thought???

I'll update this afternoon, as I ohm out the EEC connector and the EEC itself, along with resetting the timing back to 10 from 15, changing the PCV valve, and checking or cleaning the MAFS.

Thanks for any suggestions or help you wish to give!!!
 
#18
For those who may have had a similar problem, one simple way you can check the MAF, is just UNPLUG it, crank it up, ad go for a spin. You'll get a check engine light (yes), but you definitely will know if your power comes back or not.
 
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