OK, one more update of info. The sound is definitely coming from the BACK LEFT side of the engine (when standing in front of the car). I can't pinpoint the noise. About 2 weeks after the noise started, my check engine light came on: Cylinder 1 misfire. Is there a chance that the sound and the misfire are related?
I changed the spark plug out, but still get the misfire. Could the fuel injector make such a noise?
Thursday, January 19th, 2012 AT 3:56 PM