sk8erdudex

I just did aPI Swap and now my car sounds like a machine gun when I start it. It backfires really fast and then dies. I verified the timing and the firing order. What else should I check?

catch_15

Did you fill up with premium fuel before the swap? Because it raises the compression ratio.

contentsunderpressur

Does it backfire back through the intake or out the exhaust?

Derf00

Sounds like you have a leak somewhere on the exhaust side (machine gun sound) as well as some unmetered or uncompensatedair entering the intake (it dies).

steedondubs

Damn... thats messed up... im guessin you did it yourself?

96GT226410

Still sounds like timing to me. Are you getting oil to the top of your engine? Where is the backfire coming from? Leaking manifold?

72MachOne99GT

I had a nasty scary popping/snapping sound coming frmo what sounded like behind teh intake when my car had blown out a plug.

I don't know what you mean by 'checked the firing order' but im assuming at some point you checked to make sure the plugs were in securely.... if not, that could be a possibility, agian though, if the sound is coming from up in the intake region.