I recently took my beloved 628 CSi to what was supposed to be a Bimmer specialist who adjusted something under the hood that made the revs climb and fall, over and over, from 300 too 1000 when cold. After the engine has warmed it settles down, any ideas?

Mine revs to 3,000 when warm, no problem when cold.

Had the Idle Air Control Motor cleaned, helped somewhat, but the engine still revs on occasion.

Sounds more like an Audi 5000 problem!

I recently took my beloved 628 CSi to what was supposed to be a Bimmer specialist who adjusted something under the hood that made the revs climb and fall, over and over, from 300 too 1000 when cold. After the engine has warmed it settles down, any ideas?Please help?

I had the same problem. I don't know how similar the set up is for the E28 to a E24 but, I changed the fuel pressure regulator plus the vacuum line to it and it stopped.

Please help?

typical behaviour if you have an air leak somewhere after the throttle (intake). Take a spray can with brake cleaner and spray it to any spot that might be leaking. For example the area where the intake manifold mounts to the head. If the revs go up noticeably you've found the leak. Also check all those little tubes and connectors of vacuum hoses for leaks/breaks.

Wolf

Thank you very much Gentlemen, I shall give it a try :redspot

I had the same problem. I don't know how similar the set up is for the E28 to a E24 but, I changed the fuel pressure regulator plus the vacuum line to it and it stopped.

and I bet the vacuum line was leaking. The fuel pressure regulator has no influence on such "activities".

I hope that is the case because that fuel pressure regulator was expensive.

their is a website that has a ton of information for these cars, go to normgrills.net On the first page their is an option for listing by topic, click on that, a whole bunch of topics will come up, scroll down to #66 I believe, it's titled "Idle-the final word" it will tell you more than you probably wanted to know about the idle system on these cars, it talks about your condition and how to fix it. Good luck.
Dan

Also on the note of the vacuum lines. I just changed a few of them and they were a bet gummy. So they may have been collapsing and not allowing enough or if any vacuum to the units. Just a thought.