I washed my car today. I washed the under side of the hood dried everything off with an air hose too. When i was done cleaning i started the engine and it was idling ok and the then it started pulsing low. rough idle at 900 rpm. So rough the car was shimmying. Looked under the hood nothing looked disconected or broken. Dring home rpm rose to a smooth 1200 at idle. Then back down to 900 and smoothed out a bit. Stopped at a gas station to check my oil and added about a quart. It was under. idle still smooth at 900. Got home parked and the idle gets rough again. Looked under the hood and i can hear a light hissing sound on the driver side of the engine bay. fuel lines look ok. no noticable fluid leaks. no over heating. I dont know what the problem can be. Any ideas? Please help. The engine is new with only about 150 miles on it. Still breaking it in no boosting.

 

sounds like this?
<iframe width="420" height="315" src="http://www.youtube.com/embed/13Ak1UdT60o" frameborder="0" allowfullscreen></iframe>

 

Its similar yes. More of like a weird pulse. I dont have anything to take videos with. It almost sounds like a missfire.

 

probably a vacuum leak.