Strange Issue. Replace PCM?

[Bzblaine]

I've currently dealing with some weird issues with my 2003. The car will run perfect then all of a sudden, it stops running on 3 cylinders. I get the EXACT same codes everytime. P0351, P0353, and P0357. I know these are connections issues and not misfires. The problem doesnt seem to happen in park or neutral. Seems to happen most often while in drive or reverse, and stopped at a light or stop sign. Doesnt typically happen if im moving. it will last for 10 seconds to a minute, then clear up until i come to a stop again. After i clear codes, i will get the exact codes when it happens again. P0351, P0353, and P0357.

Ive replaced all the Plugs with Motorcraft. Ive replaced all COP's with motorcraft. I've swapped COPs around... its doesnt matter.. same codes. P0351, P0353, and P0357. I've soldered new COP connectors for all 8 COPs. That didnt fix the issue. Im at the end of my rope here. Any other suggestions before i try swapping the pcm? Whatever the problem is, it's only affecting those cylinders AND it's affecting all 3 at the exact same time.

 

[oktowncar]

How long will it run perfectly and then act up? is it consistent or ??

 

[etinpa]

No ideas to help but, did you notice, these three cylinders are sequential in the firing order?

Not sure if it means anything but...

 

[Bzblaine]

How long will it run perfectly and then act up? is it consistent or??

It consistently happens when I stop while in drive. Then clears up within a minute. Usually doesn’t happen in neutral

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[Bzblaine]

No ideas to help but, did you notice, these three cylinders are sequential in the firing order?

Not sure if it means anything but...

I was thinking either fried pcm or maybe crank sensor

 

[etinpa]

I'd suggest you check the connector on the PCM. The three coils that are dropping out use pins right next to each other at one end of that connector (see circled pins in the attachment).

 

[Action]

Replacing the PCM is usually the last thing to do.
There are so many steps to consider before that.

Action

 

[Bzblaine]

UPDATE: it is NOT THE PCM. I got one from the junk yard, programmed it, and I still have the exact same issue.

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[Action]

UPDATE: it is NOT THE PCM. I got one from the junk yard, programmed it, and I still have the exact same issue.

It rarely is a failed PCM. They just don't have a high failure rate.
Back to diagnosis

Action

 

[Bzblaine]

It rarely is a failed PCM. They just don't have a high failure rate.
Back to diagnosis

Action

Problem is, I can replace things pretty good. But, I have no idea how to Troubleshoot wiring issues. I have a test light and a multimeter…. And I know how to test continuity and voltage…. But that’s just about it. The problem doesn’t happen all the time so it hard to diagnose.

 

[07-TC-SL]

Inspect the entire wiring harness, take it apart, as it relates to those cylinders. Trace the entire thing back to the PCM. Inspect ground wires and points, and all connectors. A bent pin can cause issues.

 

[07-TC-SL]

If you know of a car electronics guru it might be worth paying a pro for such diagnostic if you are not electrically inclined. I wouldn't suggest the dealer or typical parts changing mechanic. Think a shop that installs remote starters, etc. - deals with wiring on a daily basis. You've effectively ruled out an issue at the cylinder itself and the PCM so it's got to be in between.

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[Action]

Problem is, I can replace things pretty good. But, I have no idea how to Troubleshoot wiring issues. I have a test light and a multimeter…. And I know how to test continuity and voltage…. But that’s just about it. The problem doesn’t happen all the time so it hard to diagnose.

Intermittent issues are the hardest to find. At least the conditions under which the event occurs is consistent.
The wiring has an issue that may be a poor ground, chafed harness or something similar.
etinpa in post #6 may have been getting close. The 3 pins being close for those cylinders is a great suggestion.
Dirt/debris in that connector can be an issue. Blowing it out with electrical cleaner may help.

The other thing about the codes is all of the cylinder are odd number cylinders. Because of that not sure why P0355 did not show up.
I bet that is some kind of clue.

The other thing you posted about is when it occurs. Has the engine moved some where it is stretching a harness because of the position of the engine?
Some loose connection (ground) is pulled too far under that condition?

Then you need a map. Ebay will have some maps for sale.
The manual will have diagnostic routines.
The wiring diagram will be the map.
You don't need know to know everything about troubleshooting. You just need to know where to go.

Action

 

[Bzblaine]

Intermittent issues are the hardest to find. At least the conditions under which the event occurs is consistent.
The wiring has an issue that may be a poor ground, chafed harness or something similar.
etinpa in post #6 may have been getting close. The 3 pins being close for those cylinders is a great suggestion.
Dirt/debris in that connector can be an issue. Blowing it out with electrical cleaner may help.

The other thing about the codes is all of the cylinder are odd number cylinders. Because of that not sure why P0355 did not show up.
I bet that is some kind of clue.

The other thing you posted about is when it occurs. Has the engine moved some where it is stretching a harness because of the position of the engine?
Some loose connection (ground) is pulled too far under that condition?

Then you need a map. Ebay will have some maps for sale.
The manual will have diagnostic routines.
The wiring diagram will be the map.
You don't need know to know everything about troubleshooting. You just need to know where to go.

Action
View attachment 20047

I will check out the connector tomorrow. I’ve checked all the grounds I can see, but I’m not sure where all of them are located. Also, if it helps, occasionally I will get p0354

 

[Freeman]

The guys are telling you the truth. The wires touch the engine somewhere and are frayed or the connector has poor contact. With the engine running, you need to open the hood and move the wiring connected to the ignition system with your hands.

 

[Bzblaine]

The guys are telling you the truth. The wires touch the engine somewhere and are frayed or the connector has poor contact. With the engine running, you need to open the hood and move the wiring connected to the ignition system with your hands.

I’ve done that. I’ve now been troubleshooting this issue everyday, 5 hours a day, for 2 full weeks. I’ve replaced connectors, sensors, pcm, wires. I’ve jiggled every part of the harness. I’ve ohm tested, voltage checked, and ground continuity checked every wire on the pcm and all wires associated with the ignition system. I’ve done scope tests. I checked for lose connections, corrosion, and damage. I’ve changed the plugs, the coils, and tested the injectors. I’ve reprogrammed. I’ve tried it all. This is an elusive issue that I simply can’t find. I finally buckled and dropped it off at a shop that specializes in wiring. They have had it for 2 days. Still waiting to hear back from them.

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[raiderfan247365]

I’ve done that. I’ve now been troubleshooting this issue everyday, 5 hours a day, for 2 full weeks. I’ve replaced connectors, sensors, pcm, wires. I’ve jiggled every part of the harness. I’ve ohm tested, voltage checked, and ground continuity checked every wire on the pcm and all wires associated with the ignition system. I’ve done scope tests. I checked for lose connections, corrosion, and damage. I’ve changed the plugs, the coils, and tested the injectors. I’ve reprogrammed. I’ve tried it all. This is an elusive issue that I simply can’t find. I finally buckled and dropped it off at a shop that specializes in wiring. They have had it for 2 days. Still waiting to hear back from them.

I feel your pain, I finally had to drop my 98' navigator at the shop due to a strange wiring issue. Spent so much time for nothing lol, slightly devastating.

 

[G-864949]

I’ve done that. I’ve now been troubleshooting this issue everyday, 5 hours a day, for 2 full weeks. I’ve replaced connectors, sensors, pcm, wires. I’ve jiggled every part of the harness. I’ve ohm tested, voltage checked, and ground continuity checked every wire on the pcm and all wires associated with the ignition system. I’ve done scope tests. I checked for lose connections, corrosion, and damage. I’ve changed the plugs, the coils, and tested the injectors. I’ve reprogrammed. I’ve tried it all. This is an elusive issue that I simply can’t find. I finally buckled and dropped it off at a shop that specializes in wiring. They have had it for 2 days. Still waiting to hear back from them.

What was the issue?