Fuel 88 LX - stalling/jerking

[jjstokes101]

Hi,

First time posting and total newbie working on an 88 mustang lx 5.0.

I replaced the fuel pump and filter, cleaned the iac, new plugs/wires, ignition coil, 02 sensors, pcv valve and TFI module. I checked the fule regulator and it is not leaking if I remove the vacuum line.

I was working on an issue where under load(in any gear) and i push it hard, once I get to 3k and up the car starts jerking like crazy. Now it is starting to stall while driving and even at idle. Could it be my pump? See attached, fuel pressure looks good and then just drops off. Any ideas?

I have replaced the battery, fuel pump and filter, cleaned the iac, new plugs/wires, ignition coil, 02 sensors, pcv valve and TFI module.

Thanks in advance.
View album 2126

 

[General karthief]

Are you taking about the drop after the engine shuts down? It's supposed to. There is a 'surging idle checklist' that will help you with idle/stall issues in the tech/how to threads

 

[jrichker]

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

 

[Mustang5L5]

As stated dump the codes and report what you get

 

[Blown88GT]

...

I replaced the fuel pump and filter, cleaned the iac, new plugs/wires, ignition coil, 02 sensors, pcv valve and TFI module. I checked the fule regulator and it is not leaking if I remove the vacuum line.

I was working on an issue where under load(in any gear) and i push it hard, once I get to 3k and up the car starts jerking like crazy. Now it is starting to stall while driving and even at idle. Could it be my pump? See attached, fuel pressure looks good and then just drops off. Any ideas?

I have replaced the battery, fuel pump and filter, cleaned the iac, new plugs/wires, ignition coil, 02 sensors, pcv valve and TFI module.
...

Sounds like you're throwing parts at it hoping one will fix it.
What makes you think it's the pump, if you replaced it?
You didn't replace the fuel pressure regulator.

 

[jrichker]

Sounds like you're throwing parts at it hoping one will fix it.
What makes you think it's the pump, if you replaced it?
You didn't replace the fuel pressure regulator.

The OP doesn't really understand what makes an automobile engine run, much less how to troubleshoot complex systems. If I remember correctly, you are an EE; how much time did you spend trying to teach other people the principles of troubleshooting electronic systems? It probably was enough that you considered it a big waste of time in most cases.

In order to succeed here on Stangnet, you have to become the auto shop or electronics teacher that they never had or wish that they had. That's what I have spent the last 18 years doing here on Stangnet. I wish you much success on your new carrier endeavor...

The next comments are intended for the OP. Blown88GT, this in not meant for you, I think that you probably are light years ahead of this guy in troubleshooting problems.

@jjstokes101 you are about to be beat with the learning stick...

Sir Joshua Reynolds' famous quotation: "There is no expedient to which a man will not resort to avoid the real labor of thinking."

Good troubleshooting takes time. Everyone seems to be looking for the magic tip that says replace this $13 part and your problems are cured. You don't have to think, dig or diagnose, just buy the part and install it. Unfortunately, it doesn’t work that way 99% of the time.
Thinking is hard work and educated thinking requires much more effort than simple parts swapping. The complexity and age of these 5.0 Mustangs works against that, as well as the number of hands that have “modified” the original design. Sometimes that modification is well done with good workmanship and other times it is mechanical road kill. It is very easy to become the victim of the previous owner’s efforts.

I spend a great deal of time trying to communicate the methodology of structured troubleshooting principles. For those who haven’t been beaten with this stick before, here they are again:

1.) Understand the system. That involves reading some books to get an overall picture of how it works. For 5.0 Mustangs, that list starts with the Chilton shop manual and the Probst book, Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.
It's about $32-$45 new, a used copy will be about $20+, see http://www.amazon.com. Select books and then select search. Use the full name or SBN number (without dashes or spaces) to do a search. Use the ISBN number and your local library can get you a loaner copy for free for 2 weeks or so.

For free automotive electrical training, see http://www.autoshop101.com/ . I have personally reviewed the material and it is very good.
Another resource is the following website by Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring: http://www.veryuseful.com/mustang/tech/engine. Study the diagrams and tech articles. There is an amazing amount of good stuff in one place for FREE.

2.) Isolate the problem. You need to be able to break the system down into functional blocks or subsystems. Once you know what subsystem has failed, it is much easier to troubleshoot. Group problem symptoms according to what system controls them.
Don’t look for a fix for ignition problems by adjusting the fuel pressure. Have an organized, step by step, approach to work your way through a subsystem before you quit and go off wildly chasing rabbits. You have three tools to use in your efforts: measure, observe and think!. Use these three tools to narrow down the list of possible failure points into a small, easily managed list of items.

3.) Install the fix. Now that you have a short list of suspected villains, plan your repair efforts so that you do the easy things first. If an item from the easy list didn’t fix your problem, then look at the high failure rate items. Spend some time here on Stangnet and you’ll get an idea of what the most commonly replaced parts are, things like TFI modules, ignition switches and fuel pumps.

If you make a change and it doesn’t relieve the problem symptoms, put it back the way it was. I have a stack of parts from where I swapped a part and it didn’t fix the problem. I put the old part back on the car and the new part went on the shelf. Someday I will either use them or trade them for something else.


Now that you have become acquainted with the learning stick, here is some help...

How the TFI ignition works in 86-93 model Mustangs:

Revised 2 June 2017 to add canned air cooling test

Tools needed: DVM, noid light, safety pin.

Theory of operation:
The TFI ignition in 86-93 Mustangs has 4 main components: the ignition switch, the coil, the TFI module and the PIP sensor inside the distributor.

The ignition switch gets power from the two yellow wires that are supplied power by a fuse link located in the wiring harness that connects to the starter solenoid.

Diagram courtesy of Tmoss & Stang&2birds

I.) The coil is mounted on the driver’s side strut tower on most EFI Mustangs. It gets power from a red/green wire and a brown/pink wire from the ignition switch. That wire from the ignition switch feeds a 20 gauge blue fuse link that connects to the red/green wire. The fuse link protects the wiring and the ignition switch, since the fuse link for the two yellow power supply wires has a much higher current rating. Without the smaller fuse link protecting the smaller wiring used in the ignition circuit, a short there would cause the red/green wire to overheat and burn up.

A bad TFI module or a bad PIP sensor have similar problem symptoms - a high speed miss on a warm engine. It can be difficult to tell which one may be the problem cause of the high speed miss on a warm engine.

II.) The TFI module is mounted on the side of the distributor and supplies the ground for the coil. Every automotive power supply circuit uses the ground as the return path to carry power back to the negative side of the battery. The TFI switches the tan/yellow wire coming from the coil to ground. It gets power from the red/green wire when the ignition switch is in the Run position. The red/lt blue wire supplies a signal to turn on more power (dwell time) when the engine is cranking. The increased dwell can cause excessive current draw if the red/blue wire remains energized when the ignition switch is in the Run position. The trigger signal comes from the PIP sensor when cranking and the computer when the engine is running. The SPOUT jumper plug enables computer controlled spark advance. When the SPOUT is removed, spark advance is locked at the setting determined by the mechanical position of the distributor.

III.) The PIP sensor is in the bottom of the distributor under the shutter wheel. It is a Hall effect magnetic sensor that senses a change in the magnetic field when one of the slots in the shutter wheel uncovers the sensor. Then it supplies a pulse that triggers the TFI module to provide a ground to the ignition coil and tells the computer to trigger the fuel injectors. A bad PIP will often set code 14 in the computer and cause hot start problems. The fuel pump control looks for the PIP pulse to keep the fuel pump control circuit turned on and keep the fuel pump running. Replacing the PIP sensor requires removal of the distributor and pressing the gear off the distributor shaft to expose the sensor. For most people, a remanufactured distributor ($55-$75) is the solution, since they may not have access to a press.

IV.) Troubleshooting the ignition system – no spark or weak spark. All the tests are done with the ignition switch in the Run position unless specified otherwise. A safety pin may be used to probe the wiring connectors from the back side.
1.) Check for 12 volts at the yellow wires on the ignition switch. No 12 volts and the fuse link near the starter solenoid has open circuited.
2.) Check for 12 volts on the red/green and brown/pink wires coming out of the ignition switch. No 12 volts, replace the ignition switch.
3.) Check for 12 volts at the ignition coil. No 12 volts and the blue 20 gauge fuse link has open circuited.
4.) Check for 12 volts at the red/green wire on the TFI module. No 12 volts and you have wiring problems.
5.) Remove the small red/blue wire from the starter solenoid (looks like it is stuck on a screw). This is a safety measure to keep the engine from turning while you are making measurements. Have a helper turn the ignition switch to Start and look for 12 volts on the red/lt blue wire on the TFI module. No 12 volts and you will have starting problems, but push starting the car will work OK. No 12 volts, replace the ignition switch. Be sure to reconnect the red/blue wire to the starter when you finish.
6.) Check the red/blue wire to make sure that it has less than 8 volts when the ignition switch is in the Run position.
7.) A noid light available from any auto parts store, is one way to test the PIP pulse. The computer uses the PIP signal to trigger the fuel injectors. The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and it will flash if the PIP is working. No flash from the noid light and the PIP is suspect. To confirm the PIP is being the source of the non flashing noid light, look for 12 volts on the red injector wiring. Good 12 volts and no flashing noid light means the PIP has failed.
8.) Remove the SPOUT plug from the harness and try to start the engine. If it starts, replace the PIP. This is a common no start condition when the engine is hot.
9.) The TFI module is a go/no go item when you have a no spark/weak spark condition on a cold engine. It either works or it doesn’t.
The TFI failure mode on a running car is usually a high speed miss on a warm engine. Many auto parts stores will test your TFI module for free. Bring along a hair dryer to get it hot while testing it and run several test cycles, since it often gets weak when it heats up.
Spraying the TFI module with “canned air” used to dust computer keyboards while the engine is hot and misfiring is one way to check the TFI. Turn the can upside down and spray away; this will cool the TFI of quickly. If it stops missing, the TFI is the likely suspect.

The coil is somewhat more difficult to pinpoint as a problem. A good coil will make a nice fat blue spark 3/8”-1/2” long. The problem is that one person’s perception of a fat blue spark looks like may not be accurate enough to spot a weak coil. The coil is cheap enough ($13-$16) that having a known good working spare might be a good idea.

diagram courtesy of Tmoss & Stang&2Birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

 

[jjstokes101]

Thanks.

Lot to go through. To start here, I was able to grab my codes.

KOER
94R
44R
33R
10

KOEO
11O
18C
10

While testing found another interesting problem. While getting in and out of the car to test, I would hit the steering wheel a bit and car stalled. Then to test it, I just put the run position and if I pushed on the wheel a bit or column, looks like power was lost, e.g. battery light would disappear. Anyone see this before? Something loose on the key ignition in the steering column?

Thanks again all.

 

[General karthief]

Tilt wheel?
key switch Or steering wheel loose?

 

[jrichker]

Thanks.

Lot to go through. To start here, I was able to grab my codes.

KOER
94R
44R
33R
10

KOEO
11O
18C
10

While testing found another interesting problem. While getting in and out of the car to test, I would hit the steering wheel a bit and car stalled. Then to test it, I just put the run position and if I pushed on the wheel a bit or column, looks like power was lost, e.g. battery light would disappear. Anyone see this before? Something loose on the key ignition in the steering column?

Thanks again all.

It looks like someone has disconnected or removed the emissions control equipment. That does not make the car run better or faster, all it does is to cause drivability problems and flaky problems that are hard to trace and fix.

However, they are not what is causing your problem. You have a code18 and possibly a bad ignition switch
Here are the things you need to fix first.

Code 18 - SPOUT out or wiring fault - look for short to ground in SPOUT wiring going
back to the computer. Possible bad TFI or defective 22 K resistor in the IDM wiring, possible bad PIP sensor in the distributor.

Use a timing light to check the timing: remove the SPOUT and observe that the timing retards at least 4 degrees. Put the SPOUT back in place and observe that the spark advances at least 4 degrees.
This code can disable spark advance and reduce power and fuel economy.

Remove the passenger side kick panel and disconnect the computer connector.
There is a 10 MM bolt that holds it in place.
Disconnect the TFI module connector from the TFI and the measure the resistance between the yellow/lt green wire and ground.
You should see greater than 100 K (100000) ohms.
Check the resistance from Pin 4 on the computer connector (dark green/yellow) and the dark green/yellow wire on the TFI connector. You should see 20-24 K Ohms (20,000-24,0000 ohms).


Resistor location: A big thanks to liljoe07 for this information:

Check over by the brake booster. Its not in the harness on the TFI, its on the main part of the harness over by the plugs that connect to the dash harness. About 6" or so from that, going back toward the EEC.

If I remember right, the resistor is covered in a shrink tubing that is sealed to the wires. So, you wont be able see any markings. The shrink tubing is labeled though. It's a 22kohm 1/2 watt resistor.

Here is the location.

Next measure the resistance between the yellow/lt green wire on the TFI module connector and Pin 36 on the computer connector. With the SPOUT plug in place, you should see less than 2 ohms.

The following is a view from the computer side of the computer connector.

This diagram is the wire side of the computer connector.

Diagram courtesy of Tmoss & Stang&2birds

Recall on Ford Ignition switches:

Revised 7-June-2014 to add Torx bit picture and source. Also added replacement ignition switch wiring pigtail picture, part numbers and sources.

Some of the symptoms of ignition switch problems are things that don’t work or are intermittent like radio, turn signals, wipers or heater.

There was a FREE recall on Ford ignition switches. They overheat and sometimes catch fire. That burns up the steering column and sometimes the car interior. Since this is very old information, you may not be able to get the switch replaced for free anymore. The auto parts stores sell the switches for $13-$15.

While you are working on the switch, check the wiring and connector closely. A replacement connector with new wiring pigtails is available from most auto parts stores

AutoZone and Advanced Auto Parts have the same Part Number: 434 - may have to order, not always in stock

Advanced Auto Parts alternate part number: PT5534

Saleen0679 was nice enough to dig this up for us awhile back: How to replace ignition switch on 1979-1993 Mustangs.
http://www.mustangandfords.com/how-to/engine/5657/

Torx bit set from Advance Auto Parts

Autocraft torx bit set – have small hole in tip for tamper proof screws.
Part No. AC571/W1386 Cost approx. $12 +tax

Diagrams courtesy of Tmoss & Stang&2birds

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg



For informational purposes, here are the emissions related codes. At a very minimum, check the vacuum lines to make sure that there are no vacuum leaks because of cracked, broken or missing vacuum lines.

Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal changes. Remember that the computer does not source any power, 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.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

Backside view of the computer wiring connector:

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


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.

connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connect the test jig or to directly to manifold vacuum.

Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).

apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

if engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
Use your finger to cap the open port on the vacuum tee.
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?
if not the EVR has failed

EGR test jig

The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.

Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. Check for a clogged air crossover tube, where one or both sides of the tube clog with carbon.

Revised 21 Sep 2012 to correct the description of the process that sets the code and include Thermactor Air System diagram.

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them.

Code 44 passenger side air not functioning.
Code 94 driver side air not functioning.

The TAD solenoid/TAD diverter valve directs smog pump output to either the crossover tube attached to the cylinder heads or to the catalytic converters.

The O2 sensors are placed before the catalytic converters, so they do not see the extra O2 when the smog pump's output is directed to the converters or the input just before the converter.

The 44/94 code uses the O2 sensors to detect a shift in the O2 level in the exhaust. The smog pump provides extra air to the exhaust which raises the O2 level in the exhaust when the smog pump output is directed through the crossover tube.

When there is an absence of increase in the O2 levels when the TAD solenoid/TAD diverter valve directs air through the crossover tube, it detects the lower O2 level and sets the code.

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:
Note that the engine must be running to do the tests unless stated otherwise. For safety’s sake, do test preparation like loosening clamps, disconnecting hoses and connecting things to a vacuum source with the engine off.

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 following computer tests are done with the engine not running.
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. Turning the ignition to Run 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.

The following computer tests are done with the engine running.
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 with the engine running. 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

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

 

[mikestang63]

TFI probably bad
ONLY get a Ford replacement one
Rock Auto sells them