P0350-P0358 Ignition Coil Fault

[Pat]

The first time, earlier this month on the 5th, out of the clear blue, driving along the highway at 65 MPH, the CEL illuminates. Pulled over and checked the codes with my XCal-2 and P0350 thru P0358 Ignition Coil A thru H are displayed. Cleared the codes and proceeded. A few weeks later, yesterday the 24th, the same thing just driving at 35 MPH in town. Cleared the faults.

The book gives an elaborate procedure for checking this fault but it assumes one cylinder at a time, not all eight.

My first inclination is a loose ground in the ignition circuit but what do I know. I had changed the plus in early July.

Anyone else experienced this?

[Zack]

Im pretty sure the coils (like the injectors) have a constant 12v supplied to them, and are then activated by a Ground signal sent by the PCM.

[RF Overlord]

Zack is correct.

The only place all 8 COPS have in common is the main connector into the PCM and the PCM itself. OK, maybe a short section of wiring harness, but unless you had some major physical damage I can't see the wires from all 8 being bad in the same place.

I'll take a look at the wiring diagram when I get home tonight, unless someone else beats me to it.

[Zack]

A coil that is BackFeeding the system can cause those codes I think.

[Dennis Reinhart]

The first time, earlier this month on the 5th, out of the clear blue, driving along the highway at 65 MPH, the CEL illuminates. Pulled over and checked the codes with my XCal-2 and P0350 thru P0358 Ignition Coil A thru H are displayed. Cleared the codes and proceeded. A few weeks later, yesterday the 24th, the same thing just driving at 35 MPH in town. Cleared the faults.

The book gives an elaborate procedure for checking this fault but it assumes one cylinder at a time, not all eight.

My first inclination is a loose ground in the ignition circuit but what do I know. I had changed the plus in early July.

Anyone else experienced this?


This fault can be diagnosed in ten minutes by a COMPETENT Ford tech using a WDS or comparable scan tool.

[Pat]

Hi Ho Dennis;

The Key words, COMPETENT AND WDS TOOL, are either both lacking or used incorrectly by the dealership here in my town.

When I had the misfire last year I took the car to my local dealer and the service writer assured me they could diagnose the problem. Their system did not give a print out, only the technicans notes on the work order.

He wrote that the car may have a bad fuel pump and/or bad CATs. I immediately bought a fuel pump from you, installed it but there was no improvement in the cars performance.

I took the car to the exhaust shop recommended by the dealership since the CATs were still under warranty. Further testing by the exhaust shop disclosed the CATs were fine.

I then took the car to a local general mechanic and he found three bad COPs in a short time. I Replaced all the COPs since the car had nearly 80K miles and problem was fixed.

The dealership could not explain why they misdiagonised the problem but kept my $65.00 fee.

After talking to mechanics that previously worked at that dealership they testified that keeping skilled technicians is a problem.

So I'm going to have to fix the problem myself are find another dealership in another city. A sad testimony indeed.

[Dennis Reinhart]

Hi Ho Dennis;

The Key words, COMPETENT AND WDS TOOL, are either both lacking or used incorrectly by the dealership here in my town.

When I had the misfire last year I took the car to my local dealer and the service writer assured me they could diagnose the problem. Their system did not give a print out, only the technicians notes on the work order.

He wrote that the car may have a bad fuel pump and/or bad Cat's. I immediately bought a fuel pump from you, installed it but there was no improvement in the cars performance.

I took the car to the exhaust shop recommended by the dealership since the Cat's were still under warranty. Further testing by the exhaust shop disclosed the Cat's were fine.

I then took the car to a local general mechanic and he found three bad COPs in a short time. I Replaced all the COPs since the car had nearly 80K miles and problem was fixed.

The dealership could not explain why they misdiagnosed the problem but kept my $65.00 fee.

After talking to mechanics that previously worked at that dealership they testified that keeping skilled technicians is a problem.

So I'm going to have to fix the problem myself are find another dealership in another city. A sad testimony indeed.


Well Pat, I have always liked you and your wife, Since I designed and built this kit, if I cant help you fix it and your shift points and make you 100% happy it's FREE, see who else on this site or any where else offers this. I will help you any way I can if given the chance.

[Pat]

Dennis;

Thank you for your kind offer.

Regards,

Pat

[Pat]

I checked the plugs, gap and COPS, all seemed OK until I started the engine and there was a definite misfire. XCal2 pinpointed #4 COP. Changed it misfire cleared.

Maybe this is the bad actor as Zack suggested.

I'll report back as time goes on.

[Zack]

Why is everyone changing COP's when the culprit is almost always the boot. :confused:

[RF Overlord]

Pat, if you get the all the codes again...

The only thing I can see in the wiring diagram that's in common with all 8 COPs, other than the +12V, are two "Ignition Transformer" capacitors, one on each side of the motor, that are connected to the common 12V supply splice that feeds the COPs. I suppose if one (or both) of them were defective or disconnected, that could trigger all the COP DTCs at the same time. :dunno: You would certainly have some voltage spikes from the back-EMF that would occur when the coils are fired.

One of them is near the back of the passenger cam cover by the firewall, the other is in the middle of the driver's cam cover, prolly on the intake...the drawing doesn't make it completely clear.

[Zack]

Those capacitors dont do squat. They are there to supress ignition 'noise', thats it.

[Pat]

I'll see if I can locate them and give a visual. Maybe in the cleaning something was discomfitted.

Thanks for your research.

[RF Overlord]

Those capacitors dont do squat. They are there to supress ignition 'noise', thats it.That's exactly my point...that noise may have been misinterpreted by the PCM as a problem.

I'm not saying this was a likely cause, just that it's possible...

[chader]

I had the exact codes after my Trilogy. No missfire and all felt good, it always came up after some hard driving. I changed the new NGK plugs to the Motorcraft(don`t recall the part number) all has been great since. My experiance says spend 32dollars and change the plugs.jmo.