Hi all. I'm happy to find the Bonneville Forum. I have a '99 SE with an issue that I can't seem to find an answer to. I bought the car 5 years back with 96k and now have 173k. When I bought it, there was a 'slight' occasional miss. When it finally got bad enough for the check engine light to come on, I had a misfire on one cylinder. I replaced the plug and wire and no help. I noticed the plug wire post on the coil for that cylinder was sort of white so I replaced the coil and the problem disappeared. After around 30k miles, the problem returned and that same post was again discolored. I replaced the coil and fixed the issue once again. Then after another 20-25k the same thing happened. This time replacing the coil only fixed it for a few thousand miles and then another replacement. Now after only 2 days the problem returned - same coil - same post. The parts guys, dealer and another local ASE certified mechanic all told me it could only be the coil. Well logically, it has to be something else. Has anyone come across this or have any ideas? ICM? ECM?
Thanks for any suggestions.

The ICM might have some corrosion on it that is causing bad voltage feed to the coil. Either replace the ICM or pull the coils off, clean it and then use some dielectric grease on it. Did you replace the wires? Bad wires can fry coils as well.

When was the last time you did a full tuneup??

Hi Kevin,
I replaced the wires the first time at around 100k and then when that and plugs didn't help I replaced the coil. I haven't replaced any wires since. Are you referring to the connectors on the ICM that the coils sits on? If so, those look very good but I haven't put on dielectric grease those or the plug wires.
I don't mind replacing the ICM if needed - just trying to not spend that much unless I have a good idea that is likely the problem. I was thinking that the ICM might either be providing low voltage or possibly too much and causing the burn outs.

Hi Mike,
What'* a tuneup? Just kidding. I changed the wires and plugs at around 100k - 75kish back but that'* it. I have new plugs to install and I think I'll run down and get a new set of wires to install tomorrow.
However, I did change them previously and the coils are still going bad.

If you've replaced the wire and still have the problem, I'm thinking that the ICM is sloppy on the voltage.

Clean up the ICM connections and use dielectric grease on all the terminals.