I have a 87 Trans Am with a Ls1/t56. It has all of the bolt ons with a TR230/224 cam. I do not have a tune. Here is my problem. The car is running like crap. It seems to run good until the car warms up, then it idles lower and backfires (sometimes very badly) and sometimes dies. I am not throwing any codes.

I have the EGR, AIR, Evap, Rear O2s, and all of that fun stuff tuned out. Could this be becuase of the open headers? I am using the LS1/Third Gen headers from Hawks Third Gen with no piping added on, just straight headers.

I also took the car around the block. Seemed to not have the power it should and ran worse as the car heated up.

The car runs and idles good if the engine is cold.

I am going to have the car towed to the shop for the exhaust install. I hope that helps.

 

A tune would probably help you alot, since you have headers and a cam. I would start there and work your way back. Also check for vacuum leaks from removing the EGR/AIR/EVAP/etc. Scan all the electronics to make sure they're working right and they didn't get knocked around with the engine swap. Are you sure everythings wired up right?

 

Fresh air is hitting your O2 sensors throwing off fueling. Get the exhaust put on and you may have to replace the O2 sensors. The reason it works well cold is because the O2's are ignored until the coolant temps reach a certain threshold.

 

Right on the money here.
The first couple of minutes after a cold start up the PCM operates in open loop mode using tables to run the motor.
Then it switches to closed loop where it looks at the O2 sensors for input.
And with the open headers the O2s are being exposed to air that isn't going thru the motor and the PCM tries to tune for this air which throws it way out of wack.

 

Not having a tune for that cam certianly will have something to do with it. Having open headers will let the O2 sensors get exposed to oxygen, make the ECM think it's lean, and it will dunp fuel like crazy.

Just courious, wherre do you live???

Re'

 

I live in MN. I have an appointmaent set up for my exhaust work!

 

Read up on engine exhaust back-pressure. You need it to run right.

 

Uh...no you don't.

 

Cool. I bought parts from a guy in Maryland who was installing a LS1/T56 combo in a 87 TA with LT headers. Kinda wierd.

Re'

 

Yeah, you dig around in the LS1 PCM long enough and you'd be surprised what you never knew.

 

Check your grounds.....

I did a swap into a 73 Z/28 and when we first got the car running on open headers it ran fine until it got warm and it ended up being a bad ground.

Good luck