Thread: need help diagnosing engine damage

okay so my car is running rough and the boost gauge on my car is bouncing around 15"-20" of vacuum,the car is popping and banging like its running too rich and the car is shaking really bad at an idle. I already changed all the spark plugs and all the ignition coils. I'm thinking bad piston rings or chipped piston and or pistons. suggestions?? i know the pulley on the supercharger is a 3.4 instead of a 3.8 like it should be and i know i ran the car kinda hard so i know that its my own fault for not doing research before i got the car.

Did any of the plugs look funny like the ends missing or anything? If you need a motor I'll have one soon I'm going to part out my gtp.

If its running that bad, it must have thrown a code already.

Either its a huge vacuum leak or the IGN module or some coil packs are bad.

i already replaced all the plugs and ignition coils,it could be the IGN but i doubt it with the way its running,ds 2 of the plugs had the ends busted off them but the other 4 were in tact but very wet with gas/oil.

Part 1 -How to Test the GM 3.8L Ignition Coil Packs.

2 busted plugs sounds like dead engine.

Do a compression test.

a compression test is on my list of things to try. any guesses on what exactly it could be?

Replace the Ignition control module, bet that solves your issue, same prob as my ssei had.

I'll try that,but i have a sinking feeling that its something internal though

Originally Posted by Nickell

Replace the Ignition control module, bet that solves your issue, same prob as my ssei had.

He said two busted plugs, ain't that a dead giveaway that he chipped two pistons?

Don't waste money before you do a compression test on any parts.

Would a chipped piston show on a compression test?

I'm not sure if it would or not,but i put a scan tool on the car and it's throwing a code for cylinder 1 misfiring. so I dont really know what the deal is because neither of the busted plugs came out of cylinder 1

on the cylinders with the bum plugs, the valves might be bent if peices of metal are flying through your engine,

like others said do a comp test

thats the next thing I'm going to do,anyone know what the compression is supposed to be stock?

alldata says this for my 07

The lowest reading should not be less than 70 percent of the highest reading.

No cylinder reading should be less than 689 kPa (100 psi).

1. Tell us what the eff you drive
2. Have you checked anything?
3. Sounds like a bad O2 or map

its a 1997 gtp 2 door,i replaced all the plugs and coils,i have all new wires for it,i scanned the car and the code is for a cylinder one misfire. compression test in my next step i think