by jondee86 » Thu Aug 02, 2007 9:18 pm
To check if the cold start idle up air valve is stuck open, when you have
the air intake ducting off, just stick your finger over the hole where it
takes its air from. That's the hole inside the throttle body on your side
of the butterfly. It's about 6 mm in dia. The engine should drop about
1000 rpm if the valve is wide open. Only maybe 100 rpm if the engine
is warmed up, and the valve is working properly.
Check the throttle butterfly is closing completely. Even a millimetre gap
will let enough air pass to push your idle way up !!!
Disconnect the cam cover vent hose from the intake manifold and
block the tube into the manifold with you finger. Does the engine speed
drop lower than it was with the hose connected ??
Check for any open tubes or holes that could let air into the manifold
or throttle body. If you find any, block them off. The only thing that can
cause an idle above 2000 rpm is air leaking into the inlet manifold.
Cheers... jondee86
1984 AE86 Corolla GT Liftback, NZ new... now with GZE
spec small port, twinscrew s/c and water/methanol injection

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