W124 1994 E200 16V IDLE PUZZLE

[jje]

Original (professional!) diagnosis; throttle body, regen valve and fuel pump relay...to cure high idle when car warmed to normal operating temp. Revs rise to 2000 when in P or N, and associated drive shunt becuase of this.

Disconnection of idle actuator plug makes car fine... 600rpm-ish idle (bar some fluctuation from lack of regulation) apart from starting when cold.

Tried new idle actuator/throtle body... no effect. Ditto effects when plug disconnected.

Tried removing plug and or pipes from regeneration valve.. no effect.

Tried removing temp sensor wire from airway leading to inlet... no effect.

30AFuse in green relay on passenger side engine bulkhead is OK. Not sure how to check this or the larger black 'kickdown' one?

Any suggestions? Feels like there could be another temp sensor somewhere that is causing it to run in warming up mode or something??
Most grateful for anything...!

 

[talbir]

When E200 is in warm-up mode, it will idle at approx 900-1000rpm. The fact that your car is idling at 2000rpm suggests it is not a warming up component which is at fault.

If you have already tried a new idle air valve, then I would suggest that it is either :

A) the throttle valve switch located on inlet manifold
or
B) you have a vacuum leak in one of the air pipes connecting to idle air valve


Hope this helps.

 

[jje]

Thanks Talbir - I presume that 'idle air valve' is the same thing as 'electronic idle actuator' as 'throttle body' ??

From your diagnosis, presumably 'B' would mean that any air leak woudn't have a noticeable effect when the electronic part of the actuator wasnt functioning (i.e. when the plug is removed and idle function is almost fine..)

Re. 'A' the throttle valve switch, where on the inlet manifold and what does it look like?! And how, practically, should its function be affected by the plugging in/out of the actuator.

I can't form a logical case for what is actually happening...