Good evening,

I'm seeking advice on a symptom-combo - for a 1991 240, 192,000 miles, automatic. Let me start with the first:

1) With the car idling, when I open the throttle *very slowly*, the revs go down for a split second before they go up. This is a small stumble, makes the engine shake a little. I can only tell when I am in the engine bay, turning that throttle pulley, it's not noticeable otherwise.

2) Sometimes, and that's very rare, the car dies when first put in gear. This only happens when the engine is cold, and barely has time to idle before engaging gear.

I did some research, which pointed to the Idle Air Control valve. This was also discussed on Car talk on Sep 5th, and they said the same thing.
I cleaned the IAC thoroughly a few months back - and I suspect it'd never been cleaned before. The air mass meter is also spanking clean, the air filter is new, and so is the flame trap (+ I have synthetic oil in it).

So my question is: could this still be the fault of the IAC? Was my cleaning not good enough? Or do I need to lube it somehow? Could it just be getting out of shape (we all do at some point)?

OR:

Could it be linked to the throttle position sensor being slightly off? I assume the TPC affects the IAC functioning.

Sorry about the novel, and thanks for your input,
Boerre