jon L Posted January 6, 2022 Share Posted January 6, 2022 A few weeks ago I started a project, replacing the rear header with a ceramic coated custom header. After a few drawbacks and cus words I managed to get it installed. After everything was back in place and secured, I started the engine and wouldn't you know it, but it had a very bad miss. First thing, I checked the plug wires to find out if I had crossed any wires. No, they were correct. Next I started to pull plug wires form the coils. Top to bottom the first two coils checked out good, but the third one had no spark. OK, I changed the coil and it still had the miss and no spark from that same coil. I was stumped for the moment. Then I had a wild idea, could the ICM be bad? On only one coil. Well, I changed the ICM. (I have extras of almost everything) My wife tells me I could build another Reatta out my parts. Any way, after changing the ICM I started the car and guess what, No Miss. Now you tell me, How could a portion of the ICM go bad while sitting. The battery was disconnected. Link to comment Share on other sites More sharing options...
Ronnie Posted January 6, 2022 Share Posted January 6, 2022 Thanks for telling us about your adventure with your car. Your thought process was very logical in the way you narrowed down what was causing the miss Good job! As for what caused the ICM to go bad while sitting with the battery disconnected is anybody's guess. Was any welding done to the exhaust system with an electric welder? If so that might have caused it. I have known electrical systems on cars to get damaged if the part being welded wasn't grounded properly. Link to comment Share on other sites More sharing options...
jon L Posted January 6, 2022 Topic Author Share Posted January 6, 2022 No, No welding was done on or around the car. I found it difficult to understand how it could have happened. And only part of the ICM to go bad. Although I am glad that it happened in the garage where I had the parts to fix it and not on the road somewhere. 1 Link to comment Share on other sites More sharing options...
2seater Posted January 6, 2022 Share Posted January 6, 2022 Do you know if the coil that was removed initially is still good? I have heard indications that a bad coil can damage the ICM under some circumstances as well as the reverse, bad ICM damages the coil. I think your title summed it up pretty well and we are still learning new failure modes. Link to comment Share on other sites More sharing options...
jon L Posted January 6, 2022 Topic Author Share Posted January 6, 2022 No, I have not checked the coil, but plan on reinstalling it in the same place and see what happens. 2 Link to comment Share on other sites More sharing options...
Padgett Posted January 8, 2022 Share Posted January 8, 2022 Anything can go bad on the shelf, particularly Delco ignitions. Best ones for me have come from yards Link to comment Share on other sites More sharing options...
DAVES89 Posted January 8, 2022 Share Posted January 8, 2022 47 minutes ago, Padgett said: Anything can go bad on the shelf, particularly Delco ignitions. Best ones for me have come from yards I've yet to get a bad one from the yard. Although the one thing that my local you pick does is mark the car "engine good" or "engine bad". They also write year and miles on the car. Makes grabbing a coil/ignition module a whole lot easier. 1 Link to comment Share on other sites More sharing options...
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