I have searched for this problem and found a few things but I am hoping someone can provide me with some more help.

I have an 87 420sel that has started to have a high idle in park and nuetral - around 1,000RPM after it warms up. Once I shift into a gear, the idle drops to around 650 or so. When I first start the car, the idle starts out at around 750 and will slowly climb to 1000 as it warms up. When it is at the 750 mark (cold and in park) and I shift to R or D, the rpms will go up to 1000 and then back down to 650 (when in gear).

I have tried to re-solder the idle control unit and have also cleaned and lubed the control valve. I have voltage at the control valve of .8v with key in run and car off to around 4v as the car warms up.

I have also replaced the 10amp fuse in the overload protection relay. Does any one have any ideas of what to check or what they replced on their car to fix a similar problem to mine. I am leaning towards the control valve but I am tring to be close to 100% sure on it before spending the $150 for a new one.

I should also add that my SRS light stays on for about 20 seconds after I start the car, but does not come on after that. I don't know if this is related or not.

Thanks in advance,

Dave W
87 420sel 168K