'99 Cavalier intermittent misfire condition on cylinder 4

[ALPO599]

My daughter's 1999 Cavalier RS has been having this intermittent misfire problem. Started a while back but seems to be more frequent now. It will run perfect than start loosing power and missing. It will do this then start running ok again, sometimes after a short while and sometimes longer periods. The engine check light will start flashing while its acting up and also the ETS OFF light will come on. Then it will stay on steady and eventually the ETS OFF lite will go out. The engine check light will eventually go out by itself but if I put an OBDII scanner on it while its still on, it puts out a code P0304, Misfire condition on cylinder 4. I replaced the plug and thought I had it but started to do it again. The wire is ok. I was thinking maybe the coil but I think cylinder 1 and 4 go off the same coil pack and no code for #1. Also thinking in the way of the injector but not sure on that. This condition isn't present all the time. It starts and runs perfect then all of a sudden it happens then clears up. Anyone have this happen or have any ideas on this??

[rruddfan21]

maybe you are beginning to lose compression due to a vlave going or something.....check compression in #4 and tell me what it is.

[inatalonIXLR8]

I agree with rruddfan21 also I would replace that wire as well. Check in the dark for shorting out, while reving engine at different RPMs.

[ALPO599]

Haven't had a chance to do a compression test but it has been running perfect for almost a week. What I did do about a week ago was check the wire for any burn marks and I already checked in the dark for any sparks and everything ok. I also took the coil packs and switched them around and jiggeled the connector to number 4 injector. Cleared the code then took it out to see if it would act up and drove it around over an hour and it runned perfect. I keep checking with the daughter and she says no problems yet. Its been running great all week. Can't really look for a problem when it's not there. Will have to just wait and see if it pops up again. Maybe it was something with those connections at the coil pack or injector.

[ARCAutomotive]

Originally Posted by ALPO599

Haven't had a chance to do a compression test but it has been running perfect for almost a week. What I did do about a week ago was check the wire for any burn marks and I already checked in the dark for any sparks and everything ok. I also took the coil packs and switched them around and jiggeled the connector to number 4 injector. Cleared the code then took it out to see if it would act up and drove it around over an hour and it runned perfect. I keep checking with the daughter and she says no problems yet. Its been running great all week. Can't really look for a problem when it's not there. Will have to just wait and see if it pops up again. Maybe it was something with those connections at the coil pack or injector.

I am having this same problem except clyinders 1 and 3 misfire at random when ever they feel like it. I changed plugs and wires, no change. I swapped coil packs and monitored misfires with a genisis code scanner, no change. I replaced crank sensor, nope not that either. I am looking into this car further monday at the shop, its not a valve as a valve would be bad at all times. I suspect either an ignition module or ecm but, when the codes trigger I get a low camshaft sensor voltage message on the scanner for a second? I need to check if the ecm output drops or if a wire maybe bad between the ecm and cam sensor. I have a module, cam sensor and ecm coming for this car and will let you know that fixes it.

[ARCAutomotive]

Originally Posted by ARCAutomotive

I am having this same problem except clyinders 1 and 3 misfire at random when ever they feel like it. I changed plugs and wires, no change. I swapped coil packs and monitored misfires with a genisis code scanner, no change. I replaced crank sensor, nope not that either. I am looking into this car further monday at the shop, its not a valve as a valve would be bad at all times. I suspect either an ignition module or ecm but, when the codes trigger I get a low camshaft sensor voltage message on the scanner for a second? I need to check if the ecm output drops or if a wire maybe bad between the ecm and cam sensor. I have a module, cam sensor and ecm coming for this car and will let you know that fixes it.

I replaced the ecm located in the passenger front wheel well infront of the tire, problem solved. (Caution) using a salvaged part will save a ton of money, I paid $50 but, the anti theft system will cause the car to start then stall, the anti theft light will flash on the dash. The fix for this is to LEAVE the key on, doors and trunk closed until anti theft light stops flashing. Turn key off and start car normally.

P.S. I replaced the ignition module using a salvaged part also at the same time however, I am convinced it was the ecm because the cooling fan was operating at startup (cold) with ac and defrost off, ignition module could not cause that.

[ALPO599]

Well, just an update. After several weeks of perfect running, it started again. This time with a code P0200 (injector circut open). As it was running real rough, I reached around and grabbed the #4 injector plug and moved it a little and it started to run smooth then when I let go it went back to running rough. Did this several times to be sure it was me messing with the plug making it smooth out. Then I shut it down and pulled off the necessart stuff to get to it and removed the plug which felt a little loose. put a small screwdriver behind the prongs and pushed them closer together so it would fit tighter; which it did. Put it back together then went to the ECM and pulled the plug that has the injector wires on it and it looked ok and put it back. Been running great so far. Will just have to wait and see if it pops up again. So far so good and its been several weeks.