Fast surging when W124 is in gear (worse in reverse), slow rise and fall of idle speed when in park.
Did the searches, (variety of theories), checked the Haynes manual (little help), and even threw a few parts at the problem (temp sensor, air mass sensor $$$). Pulled and reattached vacuum lines all over the place without any diference in the engine's behavior (as far as the surging is concerned). Bad harness was replaced under goodwill three years ago.
This was my very first post over two years ago and although I have had great success with you guys in solving my other W124 issues, this one seems to remain.
Problem hasn't worsened, but it lingers and I'm growing weary of it. Thinking of throwing the towel and shelling out $$$ to let the dealership figure it out!
To add to that, engine stumbles at first when started cold. Will stall if put in gear before a short warmup.
I would like to keep this car out of the shop if at all possible. Need to know what series of components I should be attacking for an effective diagnosis of the problem.
Help! I gotta figure this out!!!