I have replaced this coil 5 times and twice by my local ford dealer, and have replaces the connector once. When I replace the coil it runs fine for 10-15 miles then runs on 7 cylinders. It now runs on all 8 sometimes around around 2800-3500 rpm, anybody have any idea what it could be? Im at a loss.

 

This sounds like a wiring harness issue somewhere between the COP connector itself back to several leading to the PCM.

When these COP's have been replaced has anyone tested them to make sure they're actually defective or no longer working? A DC resistance test of the COP is NOT reliable FWIW.

 

Ive not had them tested because the first few cracked and spewed some weird brown stuff.

 

That condition certainly says no further testing required. What brand of COP's are being used? I'm assuming several have been MotorCraft----and the others?

If this is happening so frequently with just one particular cylinder something obviously is amiss there.

 

Ive used motorcraft, Delphi, and other after market coils..... the last couple ive put in haven't cracked and will still work once in a while at certain rpm. This is why I think it could be something else

 

Okay then with different brands and they're holding up so far I'm still suspecting a wiring issue.

BTW Coil B would also be called #2 which should be the second one back on the passenger side--correct?

This issue could also be asked in the appropriate Modular Motor forum whether V8 or V10. I'll bet someone there has gone through and successfully fixed this same sort of issue.

 

What would cause a coil to crack and leak some weird brown stuff out???????

 

That's a new one on me too---no real idea other than to consider just a defective case? I've never opened a COP or had one fail like this so the brown oozing stuff is also a mystery to me.

What concerns me more about your engine is why there would be multiple COP failures of the same cylinder. That needs to be addressed first, or so I'd think.

Please let us know if you ever solve this odd situation.

 

Unless you have a bad coil driver in PCM. Like JWA said, first check wire harness. If you don't see anything obvious then it would be computer time.