I pulled the 2.0 liter engine out of my 1984 190d and got the 2.5 liter engine from my 1987 190d in there. The 1987 engine had the ELR system for controlling the idle.

I have the complete wiring harness from the 1987 engine and will try and graft parts of it into the 84, but I was wondering if anyone has ever done this before?

At first I will have to get the car running with that system and as far as I can tell it will default to idling at 500rpm.