Electrical Random Stall Scenario 1992 LX 5.0

ppartain

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Jan 7, 2009
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My question is about a random stall scenario. This happens more so while warming up idle but it has happened driving down the road. No acting up before hand, just quits like you shut it off. Its had this for a while and I am getting knee deep in it now.
I am not completely sure what wire does what as for ignition, but here are my checks via Jrichker write ups thus far.

IDM wiring 21.7k ohms (signal back to ecu that coil is firing?)
PIP wiring .25 ohms (tells ECU it can fire coil and injectors?)
SPOUT wiring .40 ohms
TFI to pin 16) .25 ohms
SPOUT to ground OL open (>100,000 ohms) assuming meaning its not grounded.

I ran the car at idle forever Friday with zero stalls as I used my new code reader. It had an 18 constant memory code in it, I've never checked or dumped codes until this day. I cleared the codes. Rechecked to be sure it cleared them and it did.

I went back and ran the car Saturday and as it was warming up it stalled. It normally has a hard time cranking back up but sometimes it cranks and sometimes it doesn't. This time I let it sit long enough to put a noid light in and see if my PIP was sending a signal and it cranked straight back up (hard to troubleshoot being so random). Shut it back off and pulled the codes again and 18 c was back.

I removed the ECU relay from above the computer thinking if it was flakey it could be dropping out computer power. I bought an autozone relay duralast #19911 which is a 5 terminal replacement. I set my ford relay on the bench and applied 12v through the coil and had my meter across terminals 3/4 and read closed circuit, I would hold that several minutes and open/close it, hoping it may open.
Tested ford and duralast relays and both worked the same. Not sure if higher current flow through terminals 3/4 contact would potentially cause a different result, but it never dropped out.
I'll probably stick the new one in anyways. The ford measured 1.5m ohms across the coil and new one 84 ohms. Not sure if the ford has tighter/more coils or if that's a sign of a problem. Couldn't tell any working difference on bench.

My distributor is a MSD pro billet #8456 that's a solid 18 years old, including the TFI module that came on the distributor.
I had autozone test my TFI several times and they said it was good (still may have a random issue causing it to blip a signal?)
Car sits more than it should and after looking at it, the distributor looks pretty rough.
Will the PIP signal loss/flake out cause a stall out condition while its running? Hate to swap the whole distributor if its not the problem.

My ECU ground close to the starter solenoid looks good. I ordered a new MSD coil and TFI that are here now, I really wanted to prove a bad part before throwing money/parts at it.

Computer, EEC relay and Battery is out of the car so I can make whatever non power checks I need to make.

Hard to troubleshoot a random occurrence.

No wiring ever hacked, Bennett 306, Vortech supercharged, MSD 6AL/Pro distributor/Street fighter coil, 1992 LX 5.0

Any help would be great. At this point I'll have to start throwing parts at it but still wont trust it.
 

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ppartain

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I don't know what's up but I can't read your post, I'm on the dark screen and the black print barely shows.
I’m not sure what you mean by dark screen but on my cell and laptop it’s white background and black text. Shows fine on my end?
 

jrichker

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I'm with Mike - that distributor looks nasty... At a very minimum I would recommend cleaning the wiring contacts for the PIP to TFI connector.

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

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 won’t 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.
eec-iv-computer-connector-for-5-0-mustang-gif.gif


This diagram is the wire side of the computer connector.
a9x-series-computer-connector-wire-side-view-gif.gif


Diagram courtesy of Tmoss & Stang&2birds

88-91_5.0_EEC_Wiring_Diagram.gif
 

ppartain

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Jan 7, 2009
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Wow, that distributor sure looks bad. Do you have an original to swap in?
I'm with Mike - that distributor looks nasty... At a very minimum I would recommend cleaning the wiring contacts for the PIP to TFI connector.

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

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:





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.
eec-iv-computer-connector-for-5-0-mustang-gif.gif


This diagram is the wire side of the computer connector.
a9x-series-computer-connector-wire-side-view-gif.gif


Diagram courtesy of Tmoss & Stang&2birds

88-91_5.0_EEC_Wiring_Diagram.gif
Can the PIP to TFI connection (the 3 terminals) being faulty cause the random stall? I checked all the voltmeter readings.
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).

IDM wiring 21.7k ohms (signal back to ecu that coil is firing?)
PIP wiring .25 ohms (tells ECU it can fire coil and injectors?)
SPOUT wiring .40 ohms
TFI to pin 16) .25 ohms
SPOUT to ground OL open (>100,000 ohms) assuming meaning its not grounded.
 

ppartain

Member
Jan 7, 2009
73
0
6
Wow, that distributor sure looks bad. Do you have an original to swap in?
I do not, but if a random blip from PIP to TFI has potential to be the culprit, I'll sure buy another one. Just trying to possibly prove the culprit.
 

nickyb

WAIT,you now have a pair?
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Apr 3, 2009
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Just in case you are still pulling your hair out with this problem,I have gone bald with mine stalling intermittently,after much pain in the ass,I found my connected to the coil was the freaking culprit.hope you find it before you pull all your hair out.
 
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