Alright heres my ordeal. I have a 2002 3.8 with a 5 speed and 116k on it. I bought the car with a hollowed out cat and a flow master. Recently I have had a misfire problem and its been going on for a few months now. I have replaced the 1st coil pack and the ignition control module since they seemed to have burnt out. That took care of the misfire for a little while. Now it started back up again! This time I had a spark tester and found out the #2nd coil pack was misfiring. So i decided to replace the 2d and 3rd coil packs and it seemed to have worked for about 10 minutes. Now the 2nd coil pack is STILL misfiring! I have also replaced the ignition switch as well because the voltage was gradually going down when the voltage was checked in the fuse panel. What the hell is wrong with this car?! I have searched on the forums but still didnt get a clear answer. Could it be the ground wires on the car? Or is there something that I am missing? Or is the voltage regulator messin up as well? (that was checked too by AutoZone and the volts were 13.8 to 14.1)

Parts that have been replaced so far:

1. Ignition control module
2. All 3 coil packs
3. Ignition switch
4. E3 Spark Plugs
5. Spark plug wires with factory boot heat shields

 

Remove the heat shields, a GM tech told me this is a known problem point on these 3800s.

I removed mine after going through a long misfire troubleshooting process, and MSD wires have a nice longer boot standoff to the plugs.

 

Alright I had did that and these plug boots are longer than the OEs that came off of it in the first place but I am still getting the miss. I ad the spark tester connected at th coil itself with of course the other end connected into the plug wire and thats where im showing that its missing at. Could itr possibly be that if it is arcing at the block lets say where the plug is, would it still show up on the spark tester when its connected to the coil itself? Or will I have to possibly replace the PCM or ECM?

 

Alright well I pretty much have the same problem as everyone with a few exceptions. I had AutoZone coils on mine 3800 and I replaced them all with NAPA ones. Now that still hasnt fixed my problem. So all that was said and done, I have replaced the ICM 3 times all under warranty. I replaced all plug wires and plugs with E3 plugs. And STILL with the spark plug tester, im getting a missfire out of the #2 coil. I have been getting this for the last 3 months now and I cant figure it out. I dont know what else to do!!!! And I cant seem to get responses out of ppl here....

 

Scan the PCM, if there is a misfire it will identify the cylinder. You may also want to use OEM plugs, and make sure they are gapped properly. Although it is possible to get only one plug to misfire on a waste spark system like yours, in most cases the mate plug will also misfire. The scan will also identify if the KPS or CPS are acting up.

 

I had the codes pulled. It had a random cylinder misfire. Didn't specify what cylinder it is. What I don't understand is why the coil itself is missing. That's my whole problem. It's got a misfire at the coilpack. Not anywhere else. I got to find what is causing it to do that. It didn't have a code for the crank/cam sensor or the icm or even the map sensor. It had a catalyst efficiency below threshold code but that's it. Could it be the computer sending out bad signals to make the coil not want to fire randomly?

 

Random misfire is usually the result of lean fuel misture. Make sure that the wire going to #2 plug is not grounded, as that will kill the spark at both the coil and at the plug. A clogged cat can also cause random misfires as the exhausts backs up into the cylinders.

 

Thanks for all ur help. I did have a problem with my cat a while back. I dd clog up but I didn't have the money to get a new one so I took the exhaust apart and cleaned out the cat and just put everything back together. The misfire isn't a steady miss. It comes and goes as the engine is running. The spark tester shows it. I had 4 spark testers on. The 1st coil never missed. The 2nd coil for both cylinders were missing like crazy. The last coil would miss once in a while.