Hello, I just purchased a 1990 740 GL a couple of weeks ago. Pretty much everything works, but lately the car has been randomly almost-stalling when in drive at idle. On 2 separate occasions it was noticeably hard to start with a cold engine; took a while to crank, could possibly be related. But the main symptom is the random drop in the tachometer. It will just drop seemingly at random at idle and come very close to stalling, but then it instantly picks back up again.

Naturally I thought throttle body, so I cleaned it. I don't have much experience messing with throttle bodies, so I can't really say how dirty it was relatively, but I cleaned it nonetheless. Unfortunately, this did not work; it still acts like it wants to stall. It occurs randomly, sometimes when the engine is hot, sometimes when its cold. Ambient air temperature does not seem to affect it. I don't know what to look at next. Vacuum lines seem ok. Any suggestions? Thanks!

-Aaron