CEL woes

davez3v

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Like I stated in my intro post I'm no mechanic, so I'll try to explain everything as best as I can. Please excuse my ignorance.

Check engine light comes and goes on my 2005 Mustang GT. Mostly it stays on. It's always a coil issue. I tried swapping the "bad" coil to a different location, and my reader still says (for this example) coil H circuit malfunction.

Is this more than likely a wiring harness issue, injector problem or a computer issue? The car has been tuned by a local shop and runs fantastic, but this dang light will not stay off, preventing me from passing emissions.

Right now it says I have 6 bad coils. However I have no misfire.

Thoughts?

Thanks in advance!
 

Wes06

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whats the code that shows up?

It stays on H regardless of which coil you move, and its a coil specific code?
check the wiring and plug for that coil.
 

davez3v

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whats the code that shows up?

It stays on H regardless of which coil you move, and its a coil specific code?
check the wiring and plug for that coil.

yes- P0358.

But as of today it's 6 out of 8 coils "malfunctioning" it just gets worse every time the light comes on.

When it was just coil H, I swapped spots with another coil and it was still P0358
 

davez3v

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Did it have this issue before it was tuned?

no- and just to back track a bit, I used to have a 100 shot on the car. it started when it had the nitrous installed and was tuned for it. the nitrous has been completely removed for now. and retuned for n/a performance. running 93 in it, fwiw.
 

07gts197

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Hmm thats odd but if it happened right after the tune I would suspect thats the cause. What it messed up is to be determined but Im leaning towards the coil drivers in the ecu. However dont jump the gun just yet like I am lol. Have you tried pulling the spark plugs to see what kind of shape theyre in? Can you datalog? That will tell you whats going on.
 

46addict

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Did the nitrous kit use a rpm window switch? Was there any work done on the coil wires or the PCM to get rpm reference?
 

davez3v

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Hmm thats odd but if it happened right after the tune I would suspect thats the cause. What it messed up is to be determined but Im leaning towards the coil drivers in the ecu. However dont jump the gun just yet like I am lol. Have you tried pulling the spark plugs to see what kind of shape theyre in? Can you datalog? That will tell you whats going on.

I just had the plugs replaced with a new brisk set. I know what datalogging is but have never attempted it. I guess now is the time. solid thought! thank you.
 

davez3v

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Did the nitrous kit use a rpm window switch? Was there any work done on the coil wires or the PCM to get rpm reference?

I never thought about this till now. But (I think) this started when we tapped into a coil for an rpm signal for the window switch. Thank you for bringing this to my attention... again. I should have thought about this to begin with!
 

Wes06

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I had mentioned checking the wiring going to the coil first
 

stv_huff

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Is that where you are supposed to get your rpm for a window switch?
 

rickf

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RPM for a window switch? Do your windows automatically close at high RPM?
 

Gabe

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P0358 is a fault code for the PCM driver that controls the #8 coil.
If it was a P0308 it would be a misfire code for cyl #8, usually a bad plug or coil.
But the "5" being in that code may mean a bad PCM
 

rickf

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I never thought about this till now. But (I think) this started when we tapped into a coil for an rpm signal for the window switch. Thank you for bringing this to my attention... again. I should have thought about this to begin with!

Didn't it start with tapping the coil for whatever the window switch was for? I would certainly put a coil tap and a coil issue together.
 

davez3v

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I'm dropping it off at my local performance shop Monday. I shared my thoughts...well, you guys thoughts... on the matter with my mechanic and tuner. I told them to keep it till it's fixed.

I thought about getting a newer 5.0- However I won't get crap for it at trade in and it's only got 40K miles, it still smells new, and it's paid for. So, I'm going to keep it and get this figured out. Thank you everyone for the info and pointing me in the right direction!
 

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