espee1989 Posted November 16, 2011 Report Share Posted November 16, 2011 My impala started misfiring this morning, and it got progressively worse when I drove home. I was on the way home and the CEL started flashing and the car was dragging along trying to get up to adequate highway speed. I scanned and got a P0300, and I tested my coils and the bottom one didn't show anything on the tester. Is this evidence of just a bad coil? Or should I be worried about the ICM? Quote Link to comment Share on other sites More sharing options...
AL Posted November 16, 2011 Report Share Posted November 16, 2011 Try the coil first Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted November 16, 2011 Report Share Posted November 16, 2011 My impala started misfiring this morning, and it got progressively worse when I drove home. I was on the way home and the CEL started flashing and the car was dragging along trying to get up to adequate highway speed. I scanned and got a P0300, and I tested my coils and the bottom one didn't show anything on the tester. Is this evidence of just a bad coil? Or should I be worried about the ICM? A question to check on first. Was it raining and/or was the air outside moist when the misfires started to happen? On some W-body vehicles, the coil pack ignition module seals would fail over time. What would happen is that anytime moisture got in there, it would cause the pack to arc and misfire, then appear perfectly fine when the air was dry, and/or the module was dry. This is the part under the coils that the coils screw onto. Have that checked if this is the case. This would especially occur with the modules made from Hong Kong, China. Recommended that if you end up replacing it with a used coil pack, get one from a newer 3400 engine. It is fully compatible and is designed a bit better. You can also always find the entire pack (ignition module and coils) on ebay rather cheap. I hope this helps. Starflare5. Quote Link to comment Share on other sites More sharing options...
espee1989 Posted November 17, 2011 Author Report Share Posted November 17, 2011 (edited) Hmm, it was the first overcast day in weeks (I kept count because I changed my wipers about 2 weeks ago), cold and moist. It rained today and got worst. You are definitely right though, this car gave me absolute hell last winter when I first got it, so maybe its uncanny side is reappearing in the cold season approaching. I ordered a new coil for the 3800 (the D555) and plan on installing it tomorrow. On the box it says Made in Mexico... I assume the pack that is going haywire was the one that came with the car, but I don't know where the pack was manufactured but the car was put together in 2003, if that helps. Also, I know that you put grease on the two poles for the wires, but should I put grease on the contacts from the ICM that connect to the Coil? Edited November 17, 2011 by espee1989 Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted November 18, 2011 Report Share Posted November 18, 2011 Hmm, it was the first overcast day in weeks (I kept count because I changed my wipers about 2 weeks ago), cold and moist. It rained today and got worst. You are definitely right though, this car gave me absolute hell last winter when I first got it, so maybe its uncanny side is reappearing in the cold season approaching. I ordered a new coil for the 3800 (the D555) and plan on installing it tomorrow. On the box it says Made in Mexico...I assume the pack that is going haywire was the one that came with the car, but I don't know where the pack was manufactured but the car was put together in 2003, if that helps. Also, I know that you put grease on the two poles for the wires, but should I put grease on the contacts from the ICM that connect to the Coil? Ok, did you mean a single coil or the entire coil pack? Grease is not neccesarily needed, however, the coils may not be the issue, but, in turn, might be the ICM or ignition module attached to the coils. If you got the entire pack, then you should be fine, but, just remember, a single coil or the coils themselves may not have the issue. Remember that the ICM is the component under the coils and that is the component most likely to have the failure/issue. I hope this helps, Starflare5. Quote Link to comment Share on other sites More sharing options...
espee1989 Posted November 18, 2011 Author Report Share Posted November 18, 2011 Yep, thats why I made this thread in the first place, I needed some brainstorming. I am hoping its the single coil (marked for plugs 1 and 4) that isn't showing any resistance when I test it, as opposed to the ICM. I have an extra one from a botch repair last year where the mechanic slapped another icm into my car when I'm sure that the one that I bought it with worked fine (it was actually a bad crankshaft position sensor, I have a post about that somewhere). Thanks for the information, I sorta suspect some correlation with the cold weather and these problems, so I'll be observant when I put the coil in later today. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted November 18, 2011 Report Share Posted November 18, 2011 switch two coils with each other and see if the resistance test follows the coils(coil at fault) or stays in the same coil location(ICM at fault). I always use SILICONE (dielectric) grease on the terminals both where the plugs attach, and where they meet the ICM. I even had one car that had the bottom lip of the ICM shattered exposing the contacts and internals but showed no symptoms of any issue... the damage discovered during a tear down for other reasons. and yes, I get j/y coil assemblies from the top of 3100s left and right at the J/Y Quote Link to comment Share on other sites More sharing options...
espee1989 Posted November 18, 2011 Author Report Share Posted November 18, 2011 I put a new coil on about an hour ago. There wasn't a seal under the ignition coil, I suspect that might have been part of the problem. After I put the coil on, I started the car up and it seems to be working as if nothing happened. Gonna check under the other coils tomorrow to see if they are also missing their seals. Ever since I took the car to the 'mechanic' last year, the car has had a hard start. Had the spark plugs changed a few months back, hoping that the new wires and plugs would fix it, but nope, still a hard start. I turned the key after I changed this coil, and it started right up. I have hope Quote Link to comment Share on other sites More sharing options...
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