ok i dont have a clue whats causing this weird sound but i'am guessing its either the alternator or the starter, or the water pump belt. I started my car today and i got this sound like a missfire and then it cranked. Also when i was driving i can hear a sound from the front like a deep groan like you know how a free flowing exhaust sounds as you let go of the gas you hear a prrrrrrrrrrrrrr perrrrrrrr sound, thats what i hear as i step on the gas from the front, what the **** is this noise!!!!!!!!!!!

 

I got the same thing yesterday.Im guessing its my plugs getting fouled.I just put in m2 stage 3 ecu about a month ago and now my car runs quite abit more rich. I plan on setting the idle a little higher to compensate.Or just get a programable ecu. Any way thats my guess . Im just waiting till the weather clears then ill pull them and know for sure.

 

Not sure what your talkin about the prrrrrrrrrrrrrr prrrrrrrrrrr sound, but any after market intake will make your blowoff value purge really loud. DId you do this mod recentlly? just a thought

 

i dont know what your noise is with out listening to it/looking at your car, but one way to eliminate your alt. as the problem is to put a screwdriver up to it while the car is running. if you can feel the magnetic feild around it, then it is charging properly. wish i could help more

 

You could also just start the car up and disconnect the battery. If the alternator is not chargin, the car WILL turn off.

I think Sears also checks charging systems for free....

 

I don't think its your alternator. Does your car idle ok with lights on highbeam, wipers on, and radio, if so then very doubtful theres a problem with the alternator. I think you might my be on the right track with a possible problem with the airpump though. Good luck and let us know what you discover.