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Discussion Starter · #1 ·
Ok, car starts up fine and settles into a normal idle for about minute, then the rpm's all of sudden start revving between 1 and 2 thousand, just like a formula one driver would do before a start, only fast and without stopping. First, I thought it was a simple vacuum leak, but everything checks out fine. Since it takes about a minute to start to happen, it can almost rule out a vacuum leak as that would start immediatly. Could it be the coolant temp sensor malfunctioning? Seems unlikely it's a TPS or an idle stabilizer problem, as they would most likely show immediatly too. Any suggestions?
91 Passat

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2,189 Posts
Re: Idle gone beserk! No vacuum leaks though-What next? (Jettah)

it could be ur isv..
on my 92 jetta everyone on vortex said the isv.. and mine did that exact same thing
when cold it was fine but when it warmed up the idle stuck and went wonky..
try replacing ur IDLE SCREW o ring.
in the throttle body there is the idle screw, inside is a washer o-ring, mine was worn and that was my prob.
.32 cent fix to. this is kinda common kinda not... but its worth trying. way cheaper then forking out $200+ for a isv.
i went to my dealer and i told em my prob and they looked at me like i was nuts, and vdubs on mk2 forum hes a great mechanic and everyone else said isv isv or vacum leak but he went with me and isolated everything and sure enough it was something else a simple fix.
good luck
p.s the idle screw is in the throttle body, its this screw u adjust to adjust the idle rpm's up or down, see the idle screw lowers ther rpm's the isv raises it.. mine was off and loose to it was irratic..
ur problem sounds similar to mine i hope i helped.

[Modified by Tbird Pimpistik, 9:31 AM 2-6-2002]
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