HI, I've found damian and some others' posts with similar symptoms, but I really hope this is not a serious problem. Last night after I installed a racing beat catback I got from a forum member; I went to start the car, it started normally revving to 3k by itself and I blipped the gas paddle so it idles lower.

Thats when I noticed the car sounds different(not from the rb catback), sounds weird don't know how to describe will get a sound byte soon. The rpm at idle is steady at about 800, but the engine shakes strongly. When I rev the engine to a higher rpm, the engine stops shaking, and the exhaust backfires a little when I do that. After revving the rpm would drop to 200 or 100 like it wants to die, then goes back to 800. Vaccum is very low at around 9-10.

It was the first time I started the car on that day. Just the day before the car was perfectly fine(good vaccum reading, etc), and I did not even boost it. The engine was rebuild about 12k miles ago. I don't really think the catback could cause this, but just weird it happend right after I installed it.

 

Could this be cause by carbon build ups in the combustion chambers?

 

what was the idle vacuum before?

Tim

 

15-16

 

sounds like an apex seal. When I blew my apex seal it was like that too. Vacuum was at 10 and the motor rock from left to right.
You sure you didn't boost the car.? Anyways do a compression check.

 

ditto, compression test.