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-   -   rough idle/ hiss problem (http://www.peachparts.com/shopforum/tech-help/88615-rough-idle-hiss-problem.html)

john420 03-06-2004 06:04 PM

rough idle/ hiss problem
 
I have a '87 420sel which was running fine until last week. It now runs rough enough at idle to shake the car. The car runs fine at speed. There is a noticable (loud) hissing sound coming from (seemingly) under the air cleaner. I looked around the engine for any loose or cracked hoses, etc. but found none. Upon removal of the air cleaner, I believe the hiss is coming from, bear with me here, the "circular thing" that opens when the engine is revved and closes at idle.

Sorry to be so technical, :D but hopefully you understand what I'm getting at.

jeffmg1 03-07-2004 09:01 AM

The hissing sound is normal. Try cleaning Idle Control Valve. You can pull the plug off the ICV, rpm should go up to 1500.

john420 03-07-2004 07:23 PM

This hissing is not normal... It is way too loud- noticable from several feet away. Where is the idle control valve? I will check it & see what happens.

Evan 03-07-2004 09:13 PM

Check all the hoses around the intake and valve covers,,, and then check them again, the places you cant see, feel for cracks or breaks. Over time some of these hoses get brittle.. Any type of leak in the vaccum of the engine will cause the engine to run terrible


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