I have a 1997 Pontiac Trans Am with JBA shorty headers, custom catback exhaust with flowmaster muffler, SLP CAI and Spohn shock tower brace. After the install of the headers, the shop forgot to plug in the alternator regulator causing my battery to die on my way back to the shop to get it fixed. Well every since then I have had this engine resonance vibration. It didn't use to happen on startup and idle but now it does and it gets worse between 1500 and 2000 RPM's. It is really bad when I put it in drive and in reverse. Not sure what is going on and there seems to be just a slight loss of power as well. Now I did run into an EGR problem right after the headers were installed and the dealer said there wasn't enough backpressure to open and close the valve properly. There weren't any vacuum leaks or anything like that and I had them replace the valve. Not sure what is going on and I need help.

 

Is the exhaust touching anything? Sounds like maybe the headers, Y-pipe, or the catback might be touching some part of the car, creating a vibration.

Thomas.

 

I had the exhaust system installers go over the whole system and they said there was nothing wrong with the exhaust. They did however, need to make an adjustment to the headers to keep them from hitting the inside of the engine compartment but they said everything was good.

 

I have a similar vibration that occurs.
It comes and goes real fast right at 2000RPM.
You can clearly feel it althought I dont think it is a real problem. I need to provide additional support to the pipe right around the cat area. Hopefully thats it.

 

Sounds like the exhaust rubbing.

 

Well I had my car dyno tuned and they screwed up my speedo, they input the wrong gear ratio and now it says I'm going fast when really going slow. Also had them check the exhaust and come to find it's not the exhaust causing that vibration. They didn't have any ideas on what it might be but they said definitely not the exhaust. I am thinking maybe it's the torque converter? It may even be the transmission? Any thoughts gents?