Ok well Corey and I put his car together today and Everything went well we trq specs everything and all new gaskets cleaned everything and did not find any leaks. We started at about 10:15 this morning and Fired the car up at 3:00pm and found it struggles idling we hook up the tuner to find STILL the rear cylinders misfiring but this time even worse than before. So we thought we would take his penny mod out and put in his EGR and it still had the same problems. The heads just got ported and polished nothing extreme that would make it idle or run this bad. So we did a compression test on the rear cylinders to find cylinder 2=90psi (stayed level) cylinder 4=75psi (barley got to 75) cylinder 6=80psi (jumped around on the test)....So we tested the front cylinder #3 which came to 90psi (it jumped around as well. One only cylinders in the rear that were misfiring were cylinder 2,4 were misfiring.

Compression test vid
http://www.youtube.com/watch?v=dqAEkuKQcb8

Any ideas on this would be great...

thanks

This is what we have tried or original post....
tore-apart-the-gtp-are-these-heads-bad-t13008.html
possible-valve-head-problem-t11345s50.html

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Dave's Hocus Pocus Tuning of South Dakota

some pictures..

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FQUICK
CarDomain

this is at idle



Corey swapped the coil packs from one to the other and it seems to be idling and not popping anymore. THere must have been a connection issue somewhere on the coil packs or they are on the verge of going..

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Dave's Hocus Pocus Tuning of South Dakota

if any thing it looks like it is running rich


but seeing as the ran better by moving the coil packs around try swapping in known good ones and see if it gose away compleatly

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92 LeBaron Convert: Turbo 3L 97 Grand Prix GT 4dr "Frankenstein": L67 4t65 swap
97 Grand Marquis: Summer DD 99 Grand Prix GTP: Top Swap Beater

test the resistance of each coil pack. ill post the values in the morning, but theres a certain ohm resistance rating for the coils on the bottom and the top that will tell you if theyre bad.

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'05 WRX STi - COBB Stage 2|Invidia DP|3" Borla XR-1|Coilovers|Camber Plates|Swaybars|Endlinks|Bushings|Braces|Anti Lift Kit|DBA4000s|SS lines|
Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

this will seem redundant but are the plugs gapped the same and good?

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just watched the vid. that sounds exactly like when i had 5 and 3 mixed up when i changed the plug wires

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92 LeBaron Convert: Turbo 3L 97 Grand Prix GT 4dr "Frankenstein": L67 4t65 swap
97 Grand Marquis: Summer DD 99 Grand Prix GTP: Top Swap Beater

i had an issue like that on my build, took me forever to find it.

turned out to be a bad coil pack, and oddly enough, it ohmed out fine on a test.

it was a PITA too, but i eventually found it.

start from the beginning, and assume nothing. dont assume anything is "good" just because its new, or you just torqued it yesterday, etc. go back to the basics.

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'97 GT Coupe,
'97 GTP Sedan,
'97 GTP Coupe,
'96 Yukon

http://www.moradpartscompany.com
http://www.fquick.com/grandprixfamily
http://www.westcoastpontiacs.net