Hello i am sry i posted this before under my friends user-name.. i am not spaming i think he just put it in the wrong section..

The car is a 1999 Trans Am WS6, automatic, 30k miles, auto trans. Car has a pretty good sized cam (We don't know specs, it idles like an MS3) and 243 heads. Stock manifolds with one cat on the pass side, no cat on the driver side. Car is still untuned. I guess it's also relevent to know that this car was pretty ghetto rigged, he picked it up for under $5k as a dealer "back lot special" with a couple minor issues, so don't let the low miles make you think this is a pristine unmolested car, it isn't.

The car ran and drove ok since he's owned it. It always had a multiple misfire code since it is untuned. It was pretty slow, lost to a bolt on LS1 in a race but we figured it was due to the stock tune, which it may have been. Anyways, after that race he went to get the codes pulled again and found a knock sensor fault. He continued to drive the car, still ran and drove ok though. Friday night, he got gas, got back on the highway and about 3 miles down the road the car started acting up.

It doesn't want to idle, if you start it with the MAF plugged in it will run for 5 seconds then start to die. If you give it any gas at all it makes a really loud sucking noise and tries to die, with the MAF plugged in or unplugged. The intake is LOUD, like louder than the exhaust. If you try and drive the car, it struggles and will accelerate about 5mph per 30 seconds refusing to go above 1500rpm, while driving if you give it more than 10% throttle it tries to die. Oil pressure is fine. Car isn't knocking or anything bad like that. With the MAF unplugged, it will idle a lot better but still drives the same.

-We replaced the MAF, since it had a new MAF code. No difference at all.

-We then checked for fuel pressure at the rail. Immediately after shutting the car off, we checked the valve at the end of the rail. Nothing came out. At first I thought this was an issue, but someone said that is normal, that the car would lose all pressure as soon as it shut off, but I'm not sure. Anyways, we also checked all relays and fuses for the fuel pump, nothing was wrong there. Sometimes you can rev it up to 4-5k RPM if you ease into the throttle and it's in park, so I don't think it's the fuel pump?

-Next, I noticed his TPS was cracked, so I pulled the connector off. The car idled the same, and when you gave it throttle, it does the same exact thing, just makes a sucking noise and tries to die. Once it actually backfired through the intake too, if that means anything. Anyways, we swapped his sensor out for one from my car (2002 Z28). No difference, same issue.

-Next, we drained the tank thinking it was bad gas and put in a new fuel filter. The gas did look pretty dirty at first but it could have been coincidence. Ran 5 gal of fresh 93 through it and got a new fuel filter, no difference.

-Next I unplugged each coil pack one at a time. It made no difference, car still missed just as hard with no change in idle at all.

Anyone have any suggestions on this? Where should I check next? The intake being so loud is a big concern, could it be a clogged catalytic converter issue? Could a knock sensor have been working and throwing a code, but now is just 100% messed up? This is very frustrating to say the least. Thanks!!

 

Im sorry but why would your friend race his cammed car w/ one cat that hasn't been tuned?

Maybe pull the intake and check it out and pull the valve covers and check things out in there.

Some (not much) fuel should have come out of the fuel rail after you shut it off and purged it.

 

Does this have a Nick Williams or other tb with a blade stop adjustment screw? If it does, try opening the blade by an eighth of a turn or so and doing a tps relearn.

Untuned mine did similar things. I suppose it could also be the IAC motor...

 

no it doesn't.. i am out of ideas what it could be i pulled the codes yesterday.. and they were Mass air flow (which i replaced) Knock Sensor, it misfires (Prob with the cam it has and untune) and rear O2.. can i go off any of these?

 

Sounds almost like broken valve springs! I would pull the valve covers and inspect!

 

Bump.. havent tryed the Valve spings yet.. thanks

 

did you ever find the issue?

 

How about get a tune? If it has a big cam its gonna run like *** till its tuned.