I've read a lot about repairing a suspect idle speed module by resoldering cold solder joints or bad connections within the module. I pulled mine ('91 420 SEL) and removed the cover. While I don't see anything obvious needing resoldering, are there particular connections I should be looking for? There are 2 circuit boards and my guess is the pin connections to the larger one and the pin connections between the boards are most likely. Anyone know if that's right?
Also, if I screw up, will the car still start and run (albeit with very high idle) without the module connected?

J.Chip

The suspect connections are always the ones subject to mechanical stress, and you have id'd them. Look for hairline breaks areound the circumference of the pin, sometimes with some carbon from arcing. In any event, a good reflow will need the addition of some electronics flux - easiest if you just add a tiny amount of fresh rosin-core solder.

Steve

Steve,
Thanks, thought so. What about my second question. Will it run without the module in place?
J.Chip

My only MB experience is my '91 190E 2.3, so if yours is also CIS, I would expect it would run ok. Easy enough to unplug the module and try it.

Steve