when my car is at idle, i hear a constant hissing sound near the throttle body area. i'm thinking its a vac leak, anyone have any tips on how to track down exactly where it is? thanks.

 

I think I was the person that said I had the same problem, last time you posted this question. Well this is what I found out after many times taking out he intake boot, boost tubes,AFM, alot of cursing and alot of cut fingers: The hissing was normal, it came from the boost tube but it wasn't a crack. It was the idle screw. When I completely tighted the idle screw, the hissing stop, and when I opened it up the hissing started. I guess what the idle screw does is to leak some air in or out of the intake system so it can idle right.
But anyway, problem solved. I almost went crazy trying to find that damn hissing sound.
Try closing the screw all the way and see if it still hisses, mostlikely its the idle screw on top of the throttle housing. Try it out and let us know.

 

i took out the intake boot, cleaned it, cleaned afm, cleaned throttle body, checked boot for cracks/leaks, still nothing. i tightened that screw on the throttle body all the way down, the car still idled at like 850, but the hissing sound was still there. shouldnt the car idle really low with that screw all the way in? i loosened it back out a bit to where i idle at 1100k rpms. still hissing, grrr. any other suggestions?

 

Most 944/951 models idle at around 850rpm. If your car idled smoothly there, it is likely that you have no real major problem or leak.

I know a lot of people like to idle their car at around 1000-1200rpm. This seems to eliminate the shaking associated with bad motor mounts.

You might try a piece of hose, or a long screwdriver, used as a stethescope.


Hope that helps.


<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

the car doesnt idle smoothly at 850, very wavery, goes up, then suddenly drops down, then repeats. when cold the car does not want to move, and a couple months ago when it was cold outside and the engine was completely warmed up, the car would not break 5krpms and i never knew why. also it seems kinda hesitant at high rpms, it doesnt pull as hard up above 4k rpms anymore. air cleaner spark plugs ignition and coil and all that are new, any other ideas?

 

i think i may give in to the evils of turning this over to my mechanic, its a biatch to find this stupid leak. thanks for the help though.