Thread: p0300 missfire

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  1. #1 p0300 missfire 
    falcz420
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    Default 01-08-2012
    Here's the situation. I have a 98 GTP with a 175,000 on it and i get a blinking CEL when going 60-70 mph. There was a miss at WOT, and I found a bad ign wire on cyl 6 so I've changed everything on the ignition system, new Coil packs (used standard DR39), new ign mod (used standard LX364), new ac delco wires #9726RR, new ac delco plugs #41-101. Now that everything is replaced the Miss is gone the car runs like an animal but the the CEL is still doing the same thing and I'm still getting code P0300. Any Ideas? Fuel Inj maybe??
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  2. #2 Re: p0300 missfire 
    dsmuts
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    Default 01-08-2012
    If it has an all new ign system then it has to be fuel related. Try some seafoam and a fuel filter.
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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  3. #3 Re: p0300 missfire 
    Explicit_Spade
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    Default 01-08-2012
    I would check the injectors first, then pump, and worst case, Crank position sensor.
    Quote Originally Posted by W-Body Store
    Remember, GM engineers didn't take into account your need for speed.
    Daily Driver: 06 Grand Prix GT / 9.4:1 CR / IS3 Heads / Ported Gen V / ZZP Headers / HPT Pro / Pulleys: 4.25, 3.8, 3.5, 3.4, 3.2, 3.0, 2.9, 2.7
    Projects: 86 Monte Carlo SS / 98 Sonoma / 74 Honda CB750
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  4. #4 Re: p0300 missfire 
    BillBoost37
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    Default 01-09-2012
    CKPS is ~$25 and easy to swap. Fuel pump can be up to $300. I'd label the pump more "worst case" than the sensor.
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  5. #5 Re: p0300 missfire 
    falcz420
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    Default 02-11-2012
    OK, I just did a fuel pressure test at the rail and I'm getting 44 psi on key on and it stays at about the same when started and left at idle. When I put it under load it spikes to about 48 and then settles back to about 44psi. Any suggestions?
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  6. #6 Re: p0300 missfire 
    dsmuts
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    Default 02-11-2012
    Injector problem? Could be a ckps maybe.
    98 GTP modded 1.9's, sd headers, 3.4", zzp 1.0 230K miles scrapped.
    04 Comp G zzp stb's, UMI ta's, Speedbuilt sways, bully flo heads, XP, zzp headers, fsic, thrasher shift kit, 60#, 2.6" corsa 2.5", Inferno hood
    01 gt z7 turbo tep trans zzp motor
    08 g8 gt cam exhaust 11.87@118
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