99 540iA Low RPMs after driving for a while, causes jerking when stopping

[davidmx1]

I have had this issue forever. Auto Tranny. When I'm travelling for short distances it doesn't really happen, My idling RPM will stay solid at 650 where its suppose to be, but if I drive for 30-40 minutes hot my idling RPM will lower to 500 and when I'm slowing down just before I'm about to stop still the RPM gauge hand will flick down almost to 0 then go back to 500; this also coincides with a jerking sensation in the car which can be very violent sometimes. Now i use to just run my A/C and this would completely solve the issue, but now when i try to run my A/C after driving hot like this it will cause RPM issues while accelerating; The transmission won't shift up until between 3.5-5k Rpm,though this is a separate issue i believe, bad compressor? If anyone experienced something similar or has any advice would appreciate the knowledge. thanks

[Pelican Parts]

Hello and welcome to the forum! Try to pull the codes, this will give you a great place to start troubleshooting.

[Djneff]

Any lights on the dash?

[gmak]

+1

OP: Pull the fault codes. You may have some without any lights (but are there lights on the dash?). Sounds like a bit of "heat soak" as the supercharger boyz will say. Could you put KTMP on in the hidden menu and monitor engine temperature and see if that is a common factor when this occurs?

Perhaps your CCV is jammed up tighter than [insert simile or metaphor of your choice here]

[geargrinder]

Good suggests already. I think it's heat making something else surface. Something vacuum related would be plausible. A bud had similar mystery random low idle problems, replacing all the oem vac lines worked. CCV is a good suggestion too. But pulling codes first is best idea.