Low idle when warmed up

2 replies [Last post]
rkl786's picture
Joined: 24.06.2015
Location: Germany

1991 w463 230ge

Recently I have been having issue with my idle. During a cold start the idle is fine at 800rpm but after the car warms up it drops down to 500rpm. Often when this happens the car will stall at the traffic lights, or anytime when I idle. If I remove the cable to the potentiometer or idle control valve, then idle goes up to 900-1000 rpm and I have no issues when driving.

What I done so far

-Cleaned the idle control valve and also tried a new one from another car. no change

-replaced the potentiometer. no change

-Cleaned the air flow sensor. no change

Where should I go from here to fix this issue?

Thank you,

Pistonhead's picture
Joined: 17.12.2006
Location: Loughborough
GWOA Groups: Committee, Members
Re: Low idle when warmed up

Ensure you have power to the idle control valve if you have tried to substitute this unit already. 

If the air fuel mixture is adjustable have the emissions checked out and adjust as necessary.

It could mean (mileage dependent) that the throttle body needs cleaning, carbon build in this area is often and easily over looked.

Check if any engine breathing is fine and clear. 

prwales's picture
Joined: 30.05.2007
Location: West Glamorgan
GWOA Groups: Members
Re: Low idle when warmed up

check for air lieaks