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Hello everyone!

T

TurboneticsGTP

New member
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.
 


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.
 
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?
 
.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.
 


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.
 
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.
 
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
 
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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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