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[alfistjen]

Hi everybody,

I drive a 16V kat-version from '93. I first had a problem with the idle dancing around, now solved that bit by putting on another idle-engine on the manifold. Dancing is almost gone, but now another prob. When getting warm and after a bit of fast-driving the engine won't really 'drop' back tot 900 rpm at once, and sometimes it keeps hanging around 1500-2000 rpm. Could anybody tell me where to look for the solution, as it sometimes drives me mad a bit. Tried disconnecting all the kat-sensors, emission block at computer, all without big influence.
When cold it acts perfectly normal.
Other thing is I should clean out my fuel-tank ventilation. Never done that but as it sucks air when opened I suppose it could use a look at?

Regards!

Paul D.

[ZeNiTh-PbArM]

hi!

if your car doesn't come back to idle, chances are the accelerator cable or the butterflies are sticking from time to time. besides, an air leak in the idle circuitry could also cause some flow to bypass the trhrottle. be sure to check the idle microswitch too, it tells the computer to enter idle mode when throttle is released and rpm low.
concerning the tank vent, if i were you i would take care of it as soon as possible since it will destroy your fuel pump and/or will cause your tank to collapse very quickly (ask me how i know...)

regards,
zp

[Guest]

Whereabout is the idle microswitch?,and also where is the tank vent?

[alfistjen]

Hi zp,

I've checked all the hard plastic idle-bypasses, no airleak there. Still find it strange that the enigne only does it when reached full temperature. I'm very close to kick out that idle system and look for another sollution, as the problem mostly disappears by just disconneting the idle-motor for a second. Gonna need more time or a golden hint to get that bug out of my 16V. And first thing this weekend is clearing out the fuel tank vent cause indeed the fuel pump makes less noise when I open the tank. Don't wanna have the same experience of wildly 'blobbing' fueltank...

Regards!

Paul D.

[ZeNiTh-PbArM]

hi!

the microswitch is the black plastic device fitted on one of the throttle bodies, with three wires connected to it.
if disconnection of the idle control actuator solves your problem, perhaps you have replaced your faulty actuator with another faulty one? if it's secondhand, it's very likely to happen because the actuator gets stuck because of oil fumes deposits.
there is no "air vent" for the tank, but a vapour recirculation circuit. you have a canister in the rear left wing, accessible from the trunk, then some tubing that goes to the front left wing, and then some tubing to the intake manifold.
the system can be tricky to troubleshoot, because a slight amount of depression is normal, but a too important one can be the consequence of a blocked pipe or valve somewhere.
simply disconnecting the system to go back to a normal air vent is possible but make sure that the vent will not pick up some crud, water, and so on which could block it. i have myself converted my car to a normal vent but due to lack of time the tank is venting in the trunk, which smells terrible in hot weather. i will have to solve it before summer!

regards,
zp

[alfistjen]

hi,

as you metioned it I inspected the throttle body sensor. And indeed, when warm the butterflies don't return to the idle position as they where set to 'responsive' gave them little more clearance, oiled the system slightly and all fine now. Even the dancing idle stopt by solving it, the idle-motor wasn't stuck. Now to look for the bug in that vapour recirculation system in the tank.

Regards!

Paul D.