Like a sneezing sound? That is normal.

 

Yeah, it has to be normal. My car, my mother's car, and my dad's car (all M54's) all make the same noise on occasion when shutting the engine off.

 

Thanks for the input. I'll sleep better tonight. Any idea why it started so suddenly? (right after a tune-up, oil change and alternator). Just curious.

Thanks again!

 

Thats the brake booster you're hearing when you turn the car off.

 

then why is mine louder since i have a k&n 57 intake... iirc, its the intake making that noise

 

mine only started doing it loud enough to hear from in the car when i changed my intake as well, never noticed before that

 

I also noticed a volume increase when I installed my AFE. My last car with a ram air intake did the same as well

 

During my tune-up/alternator repair I pulled out my air filter (K&N) and washed & oiled it. While the airbox was open I had someone start the car then shut it off. The sneeze/chuff/pressure release sound came out of the intake with a little puff of air. Odd that it would start doing that now.

UPDATE: Now I have a dreaded "check engine" light. It's code PO174 (Bank 2 running lean). Coincidence? I've heard everything from K&N oil in the MAF to cracked intake manifold to intake manifold gasket/seal issues to "unsolvable" regarding this one. Anyone want to take a fresh shot at it? I suppose I'll start by pulling the intake manifold, checking it for cracks and reassembling with all new seals. If that doesn't work....