Thread: Hello everyone!

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  1. #1 Hello everyone! 
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    Came here looking for some help on my beloved GTP. Glad to be parts of what looks like a great forum. Any and all help greatly appreciated.

    So here goes.


    I am at a loss, I have searched everywhere. I have a semi built Turbo swapped 1997 GTP, Built the car myself, Tuned on HP tuner on a dyno twice.

    Car put down great numbers. However I have a Random misfire and it seems to be at only Idle and worse when its warmed up. Most of the time does not throw a code, I took my Timing light to all wires and the misfires are only happening on the Back 3 Cylinders, 2-4 and 6.

    1-3 and 5 fire great.

    I have Swapped Plugs, Wired, ICM, PCM, New plugs gapped properly, 10.5 MM Wires,mCoil packs.... Even bought a complete matching 97 running parts car to swap parts off, I have done EVERYTHING. I can manually pull the wires off the coil packs and watch 2-4 and 6 misfire at the packs consistently.

    Car pulls like a freight train WOT. But at Idle it randomly misses.

    Maybe a cps? or a Cam position sensor? It seems that its somewhere between the Computer and the ICM.

    Thoughts?

    What would cause this on the back 3 Cylinders??

    Appreciate the help.
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  2. #2 Re: Hello everyone! 
    Killa Bee Scottydoggs's Avatar
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    you got a cam? what plugs you running? and the gap?

    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: Hello everyone! 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    Whats the off chance that all back 3 cylinders have low compression?

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  4. #4 Re: Hello everyone! 
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    No cam yet. Plugs are gapped at .32, tuned at 16.5 pounds. I know for sure it's not a compression issue, I watched the coil packs randomly misfire at the caps as I pulled the wires one by one, also used a timing light on each wire to watch the flash.
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  5. #5 Re: Hello everyone! 
    Killa Bee Scottydoggs's Avatar
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    swap the icm to cam and crank sensor harness then. they tend to fall apart.

    32 is a bit small. 0.50 with a copper core plug would be your best bet. at 16 psi 103's would work for you.

    what type plug tho? iridium? copper? plats?

    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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  6. #6 Re: Hello everyone! 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    .045 in a turbo car sounds fine, .032 is too small if you ask me.

    You're not really going to blow out the spark with 16lb of boost. Half the blower guys use .045-.050 on 10-15lb of boost all the time.

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  7. #7 Re: Hello everyone! 
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    Autolite xp iridium from zzp. I had the plugs gapped at .50. But was told with such high boost I would get blow out. They said .32 would be best. Either way why only on the back 3 cylinders? They are all gapped the same. I will look at swapping the plugs for sure. Appreciate the ideas. No thoughts on the cam sensor? Crank sensor? Only codes I ever get is po300 and it's rare, but the misses are pretty much constant when warm.
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  8. #8 Re: Hello everyone! 
    Killa Bee Scottydoggs's Avatar
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    its compression test time too like five said.

    ever do a crank learn? if you own the hp tuner you can do it easy with that. even if you dont have a code for one, it can help it to run better.

    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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  9. #9 Re: Hello everyone! 
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    I will give the compression a check but I feel it's an ignition issue. I have manually watched the coil packs fire unsteadily on 2-4 and 6. 1-3 and 5 were firing perfect. Coil packs and icm are new as well.

    Im just wondering if it's somewhere in my wiring harness
    Last edited by TurboneticsGTP; 02-04-2017 at 09:00 PM. Reason: Misspell
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  10. #10 Re: Hello everyone! 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    Just throwing this out there but the ignition system is a waste spark so it does fire both at the same time.

    I always just remove 2 wires from the same coil pack to check the strength of the spark between the two coil terminals.

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  11. #11 Re: Hello everyone! 
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    Will do. Greatly appreciate all the wisdom.
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  12. #12 Re: Hello everyone! 
    GTX Level Member Travisgt2's Avatar
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    .32 sounds way to small
    04 GT2: 180 t-stat, cold air intake, reptile tune, plog, hv3, gt1 cam, 90#springs, new push rods, new lifters, port polished heads, lim, uim and tb, 06 Impala brakes and steel brake lines. Cosmetic: black roof rails, under glow, Pontiac ground light, blue hud dic radio controls and cluster. To come custom hood.
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