Fast idle with ASR light.

[Brian McL]

I have an intermittent fast idle, about 1200 - 1500 RPM with the ASR light on.
Not sure if it is the throttle actuator OR the throttle body potentiometer.
Car is a 91 500SL.
How do I test the actuator and/or the throttle body?
Doesn't go into limp home mode.
Just that the idle stays high, which is dangerous when trying to roll to a stop or reverse, and the ASR light is on.
Any ideas.....
Thanks

[tecqboy]

If your engine has a throttle position closed micro switch, check physical position and contact resistance.