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Discussion Starter #1 (Edited)
compression is fine, sputtering need help

ok well i havent done a compression test, but basicly the car sounds like its firing on 3.5 cylinders , it kinda softly sputters untill it hits boost, then it pulls pretty decent, i changed the spark plugs, and the wires, i havent taken it out since i changed the wires ill do that tomorrow, and try and check the compression as well, jus twondering on your thoughts about this.... im fiarly good with cars but latley ive been.... not on the ball with things to much going on to think straight so let me know what you all might tihnk is the problem, and what may fix it, im also thinking maybe exuast leak, cuz thats what it kinda sounds like... in a way
well i did the compression test, new wires, regapped the plugs to .040, and still it does it, bbut it boost ALOT better, compression was 115, 105, 110, 105, any ideas ? i suppose i should mention its a 91 GT
 

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Well first see how it goes with the new wire and the compression
 

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Discussion Starter #3
well i put the new plugs in, wasnt able to drive it till tonight tho, anyway it runs a fair bit better, boost ALOT better for sure, but it still sputters, so im gonna do the compression test tomorrow
 

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Discussion Starter #4
ok compression is this
115, 105, 110, 105, i regapped the plugs to .040 (i tihnk thats what i read anyway cuz thats what tere gapped now), runs a little better, it stil sputters
its like
brrrrrrrrrrrrrrrrrrrrrrr (rolling hte toung thing) thats kinda what it sounds like, any ideas ? the 4th plug had some oil on it too.
 

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Discussion Starter #5
anyone have ANY input on this ? i was thinking something simple like fuel pump ? the shitty battery i have, some cheapy thing i had just go get it home with 300 cca
 

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thats really low compression but its even which is the main thing, i got 150-155psi

did you crank the engine with all your plugs out and foot flat on throttle ? for 4-5 revolutions ?
 

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Discussion Starter #7
nope i left the plugs in, pulled the wires, crank it with my foot not on the gas, about 2 or 3 revolutions, i figured 110 was about right considering its turbo ? but i dont know
 

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thats probably why you're getting low numbers...

read the directions on the compression tester packaging

take out the plugs, thread the compression tester into the holes one at a time, and crank it 4-5 times while stepping on the gas. basically this starts the engine, but produces no spark, so it's like regularly starting it with the air and gas, but no fire. that should change things a bit...
 

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Holding the pedal to the floor ensures the car is getting no fuel and pulling the wire off the coil ensures you have no spark. Only then will you get the true compression numbers from what the cylinder is actually capable of.
 

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i would actually recommend disconnecting the plug from the ignitor... i actually killed my ignition coil while it was disconnected because it arced...

and i swear, the first one of you who says that it cant arc out to metal in the engine bay... ask Fastest95PGT... b/c 88626gt's car did it while we were having the MAPOC meet... we were testing HIS compression
 

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SixSick6 said:
And none of you thought to ground the coil ehhh? :lol:
um dumb???? no.. just unplugged it.... why in gods name would you ground an item that throws a hot positive charge?

tell you what damian... run a lead from your coil to ground.. and see how long it lasts
 

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AdderMk2 said:
and i swear, the first one of you who says that it cant arc out to metal in the engine bay... ask Fastest95PGT... b/c 88626gt's car did it while we were having the MAPOC meet... we were testing HIS compression
Wow, I didn't know it did that.... haha, I'm glad it didn't fry and leave me stranded that far from home! Of course there was an autozone around the corner so it wouldn't have been TOO bad....

Zalitore, I might have missed some of the original conversations, but just to make sure it was said, you checked your cap and rotor too right? I dunno if a worn cap would cause your symptoms, but it could?:shrug: Just throwin' it out there.

-Todd
 

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Any time ive done a compression test all i do is pull the EGI fuse, disconnect all the injectors. Theres no simpler way to insure no fuel or spark will exist in the combustion chamber.

Zalitore...on your distributor, where on the slider adjustment is it? if its rotated all the way either direction, your car is out of time, which could possibly be the culprit for the low compression. Could be a tooth off...they will run like that if you move the distributor...but not well.

Also, has this car overheated? alot of times once you overheat them they lose compression, the rings integrity fails and they collapse...seen it time and time again. Does the car use oil? I've also seen Idiots use felpro head gaskets or other sub-par headgaskets, and not torque them down correctly...but usually you'll see an uneven amount of compression with that type of problem.

105-115 is a pretty ominous sign theres some internal engine damage... check your timing marks...and if you can do a leakdown test.

-Eric
 

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Discussion Starter #17
i still havent had time to redo the compression test, and ill check the cap position tonight, i had replaced the wires, cap and plugs, theres oil in the 4th cylinder too, but ill retest the compression first chance i get the cars out of town at my buddys house and were doing the body work, i sure hope the car isntead dead, i only paid 300 for it :), as far as i know the car has never overheaded, its never been in the red, it started to get fairly warm when i was idling i guess my rad had a crack in the top and it was pissing out,
 
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