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Sputter/Misfire

overdose666

overdose666

New member
First off I've searched this forum for the past 2 days to try and find a solution and I still can't figure this out.

My roommate has a 97 GTP with 215k, the only mods being an HAI and ported blower. A few days ago on his way home from work his SES came on and he said the car started sputtering and surging. He took it to get scanned and was told it was a multiple cylinder misfire. So we replaced his plugs and wires and everything seem fined at idle, but the moment the car started to receive boost the misfire came back. We checked all the vacuum lines and found out the line for the bypass valve broke, fixed that yet the problem persists. I swapped all 3 of his coil packs for the ones in my 03 Monte Carlo SS (l36) and still nothing. After all this we decided to unplug his battery and on his way home from work today hes going to have it re scanned to see if there's anything new.

All the other threads I've found about the subject have either fixed it with what ive already tried or have died.

We've tried swapping out his MAF for a new one straight out of the box, and it's still being silly. The only bit of information I found on here thats helping is someone said that running the car with "no exhaust" could cause a burnt valve. Awhile back we had to replace his driver side engine mount and in the process broke one of the bolts on the crossover pipe causing a pretty bad leak. The car has a "rebuilt" engine and tranny so I'm assuming the LIM gasket has been replaced.

That's all the information I can remember at the moment, I'm sure later today I'll be able to give some more. If theres any more info that might help just let me know.
 


Doubt a crossover leak would do that unless there is no crossover on the car...even still...

Did the plugs look bent or damaged or anything when you took them out?
 
I was thinking a clogged a or broken injector, maybe a messed up connection but that doesnt explain why its fine until it gets boost, and after that is constantly off. I know the injectors go into different spots on the l67 and l36 but are the stock injectors the same? Would I be able to take them out of my monte carlo and slap em in the gtp as a test?
 
Not yet but i will once he gets home in a few hours, im trying to get together a good list of things to troubleshoot, any other suggestions?
 


Well I got her scanned last night and threw ideas back and forth with a buddy of mine.

P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem

P0300 Random Multiple Misfires

P1406 Exhaust Gas Recirculating

My buddy was thinkin its either the fuel filter or the EGR, maybe a combination of the two. He tried to convince me its probably the computer but i seriously doubt that would need to be replaced. With the P0121 code am I going to be able to fix the sensor or is it soemthing id have to replace? Today im gonna throw a new fuel filter on it and unplug the battery for a few hours to see if it helps, anyone got more suggestions?
 
Never mind, the EGR was definately causing some problems but its still throwing P0300. It seems fine at low rpms but the moment you try to push it, it bogs down...
 


Already changed the plugs and wires, really the only thing i can think of at this point is maybe there was a mixup at the gas station and he got bad gas or the wrong octane.
 
What plugs and wires did you put in?
Do you have the ability to have it scanned for misfires? (that'll tell you which cylinder)
Is the O2 wire touching the spark plug wires for either 4 or 6?
Have you checked the vacuum lines to ensure they are good?
 
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