My engine idles at around 900-1k rpm, drops to about 600 rpm with ELR unplugged. My understanding is that the ELR is supposed to increase the idle when A/C is running or the engine is below a certain temperature, so it would seem there is a problem with the ELR or one of the components that controls it.

__________________
1985 190D 2.2L 717.411 5-speed
1983 300D Euro OM617.950