Same coil keeps going bad
Posting Guru
Joined: Jun 2009
Posts: 1,908
Likes: 20
From: Fort Smith, Arkansas
Sounds like a short in the wiring from #2 coil to ground.
Someone correct me if I am wrong, but the coils are always "hot" and the PCM switches the ground on the coil primary circuit to fire them. So if the primary is always closed circuit, the secondary or high voltage side would be "on" too long and burn out.
Or you are not assembling the spring inside the coil boot correctly when installing each coil which would cause unnecessarily high resistance and heat up the secondary. Or possibly even missing the spark plug with the end of the boot when installing the coil would do the same thing. That would make a much wider arc than the .054" spark plug gap spec.
Do you have pictures of the bad coils?
Are they all burning at the same place? At the connector or somewhere else?
If the burn locations are consistent that would be a good clue to help troubleshoot the cause.
Are you using dielectric grease on the coil boot? I have seen some people on here describe the exact wrong way to use that. It only takes a very little bit on the inside of the end of the coil boot to help it slide on when installing and slide off next time when removing.
Someone correct me if I am wrong, but the coils are always "hot" and the PCM switches the ground on the coil primary circuit to fire them. So if the primary is always closed circuit, the secondary or high voltage side would be "on" too long and burn out.
Or you are not assembling the spring inside the coil boot correctly when installing each coil which would cause unnecessarily high resistance and heat up the secondary. Or possibly even missing the spark plug with the end of the boot when installing the coil would do the same thing. That would make a much wider arc than the .054" spark plug gap spec.
Do you have pictures of the bad coils?
Are they all burning at the same place? At the connector or somewhere else?
If the burn locations are consistent that would be a good clue to help troubleshoot the cause.
Are you using dielectric grease on the coil boot? I have seen some people on here describe the exact wrong way to use that. It only takes a very little bit on the inside of the end of the coil boot to help it slide on when installing and slide off next time when removing.
Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
If it doesn't recur in the same short interval as before you might have solved this rare problem. Please update us as I know this would be helpful to know for the future.
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
My suspicion is that, if you took the harness apart, you'd probably find the original wire has chafed insulation and was intermittently shorting to ground somewhere along its path. Sam was on track in post #17 with that idea. Such an intermittent short to ground would cause the coil to be conducting for far longer intervals than it was intended to and it subsequently overheated internally and failed.
I would note that a failure inside the PCM could do the same thing but it's a lot harder to get in there to repair.
Good job!
I would note that a failure inside the PCM could do the same thing but it's a lot harder to get in there to repair.
Good job!
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