Thread: Need help with a P0300 code

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  1. #21 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    I just got done swapping over my coil packs and ICM from the Pontiac to the Impala. It's still misfiring, and I know those parts are good. Any other ideas? Anyone know if the computer would throw a code if the crank position sensor was bad?
    Last edited by derpyimp; 05-28-2018 at 12:44 AM.
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  2. #22 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    Also, here is a scan of it misfiring at WOT. You can see where the engine RPM starts to struggle and the MAF readings match it.

    http://i346.photobucket.com/albums/p...psgkpl64zm.png
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  3. #23 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    Just pulled all the spark plugs, regapped them from 0.060 to 0.045 and reinstalled them. Still misfiring badly, now even at idle.
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  4. #24 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    Tried taking off the oil fill neck while the car was running to see if the engine reacted at all. It didn't do anything. Also no noticeable coolant loss, so I don't think it's the LIM gasket. Tried unplugging PCV while it was idling, then driving around to see if the valve was opening too much. Still missed. I'm running out of ideas lol
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  5. #25 Re: Need help with a P0300 code 
    GrandPrix Junkie SgtMarshal's Avatar
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    I'd go smell the exhaust, if the catalytic converter is bad it will smell like rotten eggs.
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  6. #26 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    Just tried it, smells okay to me. The car also doesn't feel sluggish like a clogged cat would do to it. It just starts missing really bad.
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  7. #27 Re: Need help with a P0300 code 
    Killa Bee Scottydoggs's Avatar
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    pull the o2 sensor out the manifold, then drive it, if the misfires stop or are reduced, its a cat.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  8. #28 Re: Need help with a P0300 code 
    Turbo is the way to go. BillBoost37's Avatar
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    good test for a cat there.
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  9. #29 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    Just tried it. Still missing really bad. The car actually died when I was pulling it back into my apartment's parking lot, though that may have been because it was missing the sensor lol
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  10. #30 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    I found a new clue. When I start the car, it will idle normally at first. Then, after a minute or so, the idle increases to around 1300 RPM and it starts misfiring. Is this the EGR turning on or something else the computer does shortly after starting the car?
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  11. #31 Re: Need help with a P0300 code 
    SE Level Member derpyimp's Avatar
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    I think I figured it out. When I swapped the transmission, there was one ground on the transmission toward the front of the car under the front manifold/crossover pipe connection that I apparently did not tighten down enough. I guess the connection was flaky enough to cause electrical issues, which would explain why my misfire was intermittent. Once I got the nut holding the grounding wires tightened down properly, I had zero misfiring. Stupid simple fix.
    '04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian
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  12. #32 Re: Need help with a P0300 code 
    GTX Level Member cheatah faheatah's Avatar
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    Thank You.
    For the record : I am NOT a naked meth-head who shoves rocks up my butt.
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  13. #33 Re: Need help with a P0300 code 
    Killa Bee Scottydoggs's Avatar
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    the old loose ground cable strikes again lol glad to hear it was a free fix in the end.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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