Hi, my 2001 1.9T just started making a single popping sound when I start the engine cold. No noise when the engine is warm. The sound seems to come from the rear of the car (i have to try finding the spot with someone else starting the car). Is this a misfire? If so, what can be causing this? I just flushed my engine with swepco 503 flush (via a manifold vacuum hose as directed). The noise started happening a few days later. Is this related? Check engine was already on due to a CVVT reset code (camshaft reset valve error) which i was trying to fix via the flush. So I don't know if anything is being picked up by the cpu. Any ideas? Help!
Thanks

 

Is it coming out of the exhaust?

 

I stood behind the car this time and hadsomeone start it for me. It seems to come fromthe area near the rear right wheel. It does not sound like it comes out of theEND of the pipe... but near the rear (possibly still in the pipe). I have to wait another day now to try again
Thanks for your help!

 

oes it crank along time before it starts after sitting for a while?

 

Actually no. It startsquicklylike it would when it's hot. Just a pop as soon as the engine catches.

 

Maybe an exhaust mount is broke?

 

I think it's comming from the catalytic converter... My check engine turned off and has not come back even after a few more pops (so idon't thinkit's a misfire anymore - but then again i dunno). Is it possible that the smoke from the flush damanaged something in the converter? Is this dangerous?

Thanks again!

 

First I would have the codes pulled.
Next check the fuel pressure regulator to make sure it isn't bad and leaking fuel into the intake/engine.