Fast idle on 1988 5000tq

[Leah Mueller <muellerl@cadvision.com>]

Dear Jeff,

I just had the same problem with my 86 5000 CD turbo.  After having a
leaking hose fixed, the idle went up to the same as yours.  My mechanic said
the idle stabilization valve (the small 4 inch silver cylinder sitting just
behind the throttle assembly) was probably working over time and may have
gotten dirty or stuck or both.  Its an expensive part so he suggested that I
take it off, clean it first with methal hydrate to get rid of any water or
ice, and then clean it all out with WD 40.  It works just fine now, good idle.

Assuming you have checked for vacuum leaks, first give your idle
stabilazation valve a love tap with the plastic handle of a screw driver.
See if the vibration knocks it loose.  The tapping didn't help me.  Give it
a good cleaning out and I hope you have good success.

David