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Thread: misfire troubles post here (Resolved Misfire Issues Only)

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    Thumbs up misfire troubles post here (Resolved Misfire Issues Only)

    I see allot of people have the similar issues with ignition problems, and getting P0300 and P0301-4 codes. Since these posts are all over, I figured we should pool our experiences in one place.

    please tell us...

    1.how your problem started, was it intermittent, did you pull the codes, what ones did you have?

    2.how it progressed ( better worse on its own) how long did go on before you had to change out parts
    .
    3.what steps you took to solve the problem. parts replaced...did you do several at once or separate components, any particular order? (ICM, coil, plus wires) how did you test what to rule things out?

    4. what engine upgrades to you have? IE valve train, intake, exhaust, pistons, rods, did you go to forced induction on an N/A motor.


    and as always...try to keep it on topic, and if you think I left something out of this post that should be added to the list PM me and I'll edit it and add it in.
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    Misfire Detected 2004 Malibu

    My misfire problem started small. I really thought it was just a hiccup of the transmission or my foot slipping on the pedal a bit for a long while. I'd just get a little bump once in a while. Say, every 500 miles or so. Then, a couple times it began bucking really bad with NO power. Realised later that the CAT was getting red hot.

    The problem is very very erratic. I have driven 20 miles to work thinking it was ok only to have it go bad half-way home. I have had it go bad on cool mornings and hot afternoons. The only somewhat constant is that I can pretty much be sure that it will go bad if I really stomp on it for a while.

    I have:
    Changed plugs and boots.
    Inspected hoses and listened intently for vacuum leaks.
    Found intake past the throttle coated in thick oil. Cleaned it out with throttle cleaner in a can.
    Decided the intake had a vacuum leak, so I changed intake gaskets. During that, I found that the entire intake manifold was coated in the oily mess. This oil I am 99% sure has come from the PCV vent in between #2 & 3 intake ports. I think this b/c the oil mess was evenly dispursed to all four runners and did not reach (was not from) valve guides.
    Took it to the dealer and paid for a diagnosis. They said it was the ICM. Replaced it today and found that they were wrong. Went back to talk to the dealer shop about how they concluded it was the ICM. Apparently the mech just followed Service Instruction PIP3433D which says that (unless there is a short) P0300 can be fixed by replacing the ICM.

    Update 5/11/09
    Looked further through the forums here and found many people who had either the ICM or coils causing their problem. Also found a sticky posted by Maven with the ignition schematic. Using this, I found the correct pins on the coil assy to probe with my Ohmeter. The seconday coils were both reading in spec (4-8K Ohms) at 4.4K Ohms. Cylinder 1-4 Primary coil was in spec (.4-.8 Ohms) at .6 Ohms. Cylinder 2-3 was initially in spec at .6 but when I touched the probe to the pin again it read .8 Ohms. I touched several more times and the resistance rose quickly to 4, 20, 50 and finally in the hundreds of Ohms.

    Replaced the coil assy and the car no longer misfires. Unfortunately, it is throwing code 420. I assume that I destroyed the CAT from all of the misfires.

    If you get misfires detected, checking resistance on the coil assy is a VERY easy proceedure. Takes only about 20 minutes.
    Last edited by zachtb; 05-12-2009 at 10:39 AM.

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    P0300

    Ran fine when I drove to work. Went to leave 10 hrs later and it was hard to start. When it did, ran rough, no power......sounds familiar. I have changed the plugs, "wires", coil pack, cat converter, both up/down stream 02 sensors and I have an ignition control module on order. My converter did blow it's guts out so that needed changed. Thought it would help. Looked at the timing chain to make sure it didn't jump on me but I am confused as hell by the different colors I have been hearing about. I have GREEN/RED links in my chain. I've heard purple/blue/silver. I just want this car to work. It only has 53000 miles on it. Any help would be appreciated.

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    i had the same thing with my cavalier... i got a post here somewhere... happened like twice a month... went i hit the gas it "stumbled" and when it picked up it didnt have a lot of power... when id let off the gas it stumble again... put it in neutral and turn it off then start it back up and it was fine for another two weeks... i have a tech 2 and monitored the car when it was messin up but couldnt tell anything .. no voltages dropped on sensors or anything... i put a new exhaust on the car... went about 20 days thinkin it was a clogged cat and then it started again lol.. id have a raw fuel smell commin from the exhaust in the mornins but always thought that was normal..... i never figured it out.. still did it til i totaled it... started at about 60,000 miles

    heres my original http://www.ecotecforum.com/forums/sh...7244#post97244
    Last edited by Cinpro; 07-05-2009 at 06:54 PM. Reason: compact thread

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    My 06 with over 300,000 miles on it threw a code for misfire after replacing the oxygen sensor.
    It turned out it was the ignition control module.
    The coil pack was ok.

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    2003 sunfire with only 69,000km, I had no code problems until after I installed the level zero tri flow camshafts....I now get p0300 random engine misfire code, it trips only about once a month...haven't done much to diagnose yet.


    My Sunfire Shakes, Rattles, and Rollzzz...

    Mods: Wai, Upper/Lower poly mounts, 4-2-1 header, LZM camshafts, 2.4L intake man., 32lb Cobalt SC injec., BDK kit (soon), Revtronix ECU tuning, 2.5" full exhaust with 2.5" cat, resonator, Dynomax ultraflow ss muffler ***** Eibach front/rear sway bars,Poly control arm bushings, TTR subframe brace, front/rear upper strut braces, 1.2" Suspension techniques dropsprings

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    well i got a tip awhile back for tuning that all but solved it for me, no knock, no CEL, and only a slight reported misfire while logging. GM's base spark tables are set up a lil funky, once I set the base spark vs ECT to all 1.0, and adjusted my VE a couple of times to bring everything inline its been fine and I have more power.okay i need coffee now i say now !!!
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    I went to start my car, but it wouldn't start. I figured it was the GM security system, but the light never came on. After cranking it 3 times or so, I gave it a shot of gas, and it caught. I then got a really rough idle, to the point where me steering wheel was shaking a bit. The SES light then came on and proceeded to blink, and the trac off light also came on. I tried the changing the spark plugs, didn't do anything. Brought it to a garage, and when they scanned it they pulled a P0300 Code, Multiple Misfires. On the mechanics advice, we got a used coil pack and tried that, and sure enough the car is fine again.
    -2002 Pontiac Grand Am SE Coupe

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    With symptoms that bad usually the coil packs fixes the problem, but when you get the p0300 much less frequently and nothing appears to be going haywire... its much harder to diagnose.


    My Sunfire Shakes, Rattles, and Rollzzz...

    Mods: Wai, Upper/Lower poly mounts, 4-2-1 header, LZM camshafts, 2.4L intake man., 32lb Cobalt SC injec., BDK kit (soon), Revtronix ECU tuning, 2.5" full exhaust with 2.5" cat, resonator, Dynomax ultraflow ss muffler ***** Eibach front/rear sway bars,Poly control arm bushings, TTR subframe brace, front/rear upper strut braces, 1.2" Suspension techniques dropsprings

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    Just logging in with update on my car. 420 code was still tripping last time I was here. i got a new CAT, and that fixed the problem.
    Just want to say again that checking the Coils with an Ohmmeter is very very easy. Checking the coils by putting in new ones is even easier, but much more expensive.

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    Gamer IDs

    Gamertag: Cogent Design
    I have a theory: I think a misfire can be caused by trying to idle very large injectors. Telling the injectors to have a very very very short pulsewidth might cause them to act funny and cause a misfire. What do you guys think?

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    yeah if the injectors can't make a small enough pulse width it could be dumping too much fuel, but in theory you should be able to tune your idle VE down to get itmore under control.
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