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  • Another Misfire Thread

    98 3.8L @ 65k

    Ok I have done a lot of searching both here and another forum. I have noticed a lot of v6 camaros with misfiring problems. So I will contribute mine as well...

    Monday morning I went to leave for work and my SES light was on at the turn of the key. Sunday night the car was fine. Go down the long driveway and nothing seemed to be wrong except the SES was on. Go get on the highway and get the car up to speed, set the cruise and still nothing. Start getting to the hill and the cruise starts to apply the accelerator and the car starts missing, backfiring and rattling violently and the SES starts blinking. So i back it off and baby it, the blinking stops but SES remains on. As I get closer to work the situation gets worse. Leave work, the problem seems intermittent when the car is cold and constant when the car is hot. Go to Autozone by work and they tell me its a p0304 - #4 cylinder misfire and it is showing up twice on their scanner.

    No big deal. I go inside and buy plugs and wires. Go home and diagnose a few other things before I change plugs and wires to see if I am able to return them. I am cheap what can I say.

    The #4 injector passes the ohm test at about 12.4 ohms. #4 wire passes the ohm test at about 28,000 ohms. I also took an old plug off the bench and through it into the #4 wire and there was spark. The spark did not seem as strong as it was through #6 wire but that could have just been my thinking. Not sure. Have to limp it back and forth to work Tuesday.

    Change the plugs and wires eventhough the resistance test passed. All the plugs look normally used except #4. It had noticeably been arcing on the ceramic but it wasnt wet like i thought it would be from the misfire?
    Under closer examination I notice a slight crack in #4 plug. I gently pick at it and the plug breaks in half. Must have been the problem right?

    Well get everything together, disconnect the battery to clear the codes and then take it for a road test. Seems to drive just fine for the first leg of the trip. One little sputter leaving the driveway. Let it warm up and then jump on it a few times and everything still seems fine. Except when the car is under high load in high gear. Then it has the missing feeling but it is far more intermitant and stretched out than it was before. It is also not throwing any codes now. The SES light has not been on since I changed the plugs and wires.

    So where do I go from here? Is there a way to test the coil packs other than switching them? I am not getting a code now so if I switch packs, i will have no way of narrowing the misfire down. How likely is it that the injector passed the resistence test but is still the problem? I am also not getting an 02 code. I can check and see if the cat got junked up from running with a miss for two days by seeing if its "red hot" right? Will the cat clear out any possible unburned fuel that made its way in or does the cat just junk itself?

    Other than that I am at a loss of ideas. Any suggestions would be helpfull. Thanks.

  • #2
    Re: Another Misfire Thread

    The next 2 things on my list would be the coils, and the ICM. I know it may sound dumb, but did you double and triple check you didnt have any wires crossed, and that they were seated properly.

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    • #3
      Re: Another Misfire Thread

      Originally posted by lilchubby View Post
      The next 2 things on my list would be the coils, and the ICM. I know it may sound dumb, but did you double and triple check you didnt have any wires crossed, and that they were seated properly.
      No not dumb at all man. Its a valid suggestion really. But yea I am sure there arent any wires crossed. They were all changed individually. Old one came off and new one went straight to the plug. Yes they all "clicked" on and I put some tension on them to make sure they were attached and then pressed back down on them to double check.

      Is there any way to test the ICM?

      One thing I was just thinking of... the gap is supposed to be .060 right? The plugs came gapped at .055 and I regapped them at .060. Oh and they are NGK V-Power plugs

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      • #4
        Re: Another Misfire Thread

        autozone can test your icm

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        • #5
          Re: Another Misfire Thread

          I have a miss fire to, how'd you test the injector? I've narrowed down to the cyl, but unsure of coil or injector. Thanks for thread, may help a few people.

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          • #6
            Re: Another Misfire Thread

            Or spark plugs
            Leonard
            www.fquick.com/96V6Junkie
            sigpic

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            • #7
              Re: Another Misfire Thread

              Originally posted by BLAZER87 View Post
              I have a miss fire to, how'd you test the injector? I've narrowed down to the cyl, but unsure of coil or injector. Thanks for thread, may help a few people.
              Pull the electrical connector off and use a multimeter on it to test the resistence. It should be between 11-14 ohms.

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              • #8
                Re: Another Misfire Thread

                OK well after a weekend of working on the car, the situation did not get any better.

                Changed plugs and wires.

                Changed injectors.

                Changed coils.

                Tested ICM. Tested strong.

                Cleaned EGR and PCV.

                Fuel pressure is good.

                Tested injector connection with a test light. Injector is firing.

                Sprayed carb cleaner and propane around intake manifold. No change in idle.




                Anybody else have any other suggestions??? I am about out of ideas.

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                • #9
                  Re: Another Misfire Thread

                  Originally posted by Frechles71 View Post
                  Pull the electrical connector off and use a multimeter on it to test the resistence. It should be between 11-14 ohms.
                  Thanks, pulled 2 injectors to test, good one, bad one, both tested at 13. I sprayed them good with FI cleaner, then reinstalled...miss now gone. Guess I had some debris in the bad one, working fine now!
                  If it's still the same cyl, could maybe a lifted be sticking keeping the valve oepn or maybe a burnt valve? I would have tried all you have, I would be lost at this point also.
                  My 99 Tahoe has what feels like a constant miss. I put a scanner on it, everything is showing normal, no misfires or any history. just getting used to it now.
                  good luck

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