Thread: 04 gtp misfiring at 3/4 to full throttle

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  1. #1 04 gtp misfiring at 3/4 to full throttle 
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    hey guys just picked up an 04 gtp had many of the 98-2003's but cant seem to track down my misfiring issue on this 04.

    things ive done.
    1. changed to steel lim gaskets.
    2. new plugs and wires.
    3. checked vacuum lines.
    4.cleaned tb.
    5. new fuel filter.
    6. new air filter.
    7. drilled holes before cat to see if it was plugged no difference.

    i have no cel, however a couple days ago i got limp mode with code p1516 but has not been back since. dont dare throw a 100 accel pedal at it til i could be certain thats whats causing it to spudder terrible under 3/4 to wot you can run slight boost pulls good. till you hit that 3/4 mark then just sputters out. car is completly stock even stock airbox. anyone have any more ideas? idles great. 91 oct only been in it.
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  2. #2 Re: 04 gtp misfiring at 3/4 to full throttle 
    Killa Bee Scottydoggs's Avatar
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    could be a bad coil. or icm.

    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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  3. #3 Re: 04 gtp misfiring at 3/4 to full throttle 
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    i see the 6/3 coil has been swapped and the 1/4 2/5 are the original. i should have specified it does have 253k on it....
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  4. #4 Re: 04 gtp misfiring at 3/4 to full throttle 
    Killa Bee Scottydoggs's Avatar
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    bad injector can also cause the misfire, if its on one cylinder. if its on a shared coil, icm or that coil.

    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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  5. #5 Re: 04 gtp misfiring at 3/4 to full throttle 
    GXP Level Member GTPpower's Avatar
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    Can you live Scan it to see what cylinder is missing?
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  6. #6 Re: 04 gtp misfiring at 3/4 to full throttle 
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    unfortunately, i dont have a way to live scan. what im figuring is it sounds like i got 2 cylinders cut out, one is pretty distinctive vs 2 cylinders. being it has that many miles it could be a number of things.
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  7. #7 Re: 04 gtp misfiring at 3/4 to full throttle 
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    Quote Originally Posted by rileychris View Post
    unfortunately, i dont have a way to live scan. what im figuring is it sounds like i got 2 cylinders cut out, one is pretty distinctive vs 2 cylinders. being it has that many miles it could be a number of things.
    i did ohm out the injectors they all come back at 13.0 to 13.2 ohms forgot to add that up top in the original post.
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  8. #8 Re: 04 gtp misfiring at 3/4 to full throttle 
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    ok so i got the studdering figured out, it was in fact the ICM so if anyones getting the same issues, hope this post will help you out. thanks for the help guys
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  10. #9 Re: 04 gtp misfiring at 3/4 to full throttle 
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    Bad tac or bad communication wire between the tac and pcm... Do you have any U codes? If not then prolly as bad tps but you have to replace the tac because the tps can't changed seperate
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