Hi,

Can somebody give me a run down on how idle control works on the OM606.910?

A couple of years ago I spent some money with a dealership to try a rectify a highish idle issue.

When car gets to approx 90-95C on the gauge my idle goes from about 600rpm to 850rpm and when the car temp drops back to 85C so do the revs, back to 600.

They never did find the cause and I needed to get the car back on the road. I can see where they did some fault finding:-

At the main wiring harness plug connection (behind the battery) they cut a wire out of the plug from both sides, essentially bypassing it from the plug all together; possibly to do some current testing on the circuit. It is still bypassed from the plug but soldered together with a hand written label saying 'idle circuit'.

I guess there are two questions I'm asking here:-
-A run down of how the idle works and
-What testing could I possibly do to hone in on the problem

As always, many thanks.

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1995 E300 Diesel