Intermittent idle surging

[Lirker]

Hello so I have a 325i engine that will drive great one day, then the next day I start it up and it surges instantly going from 800-1500 and doesn't stop until I turn the engine off and mess with a few things in the engine bay. Sometimes it works, sometimes it doesn't. Specifically I mess around with the cables involing the brake booster which I think where it was coming from. I recently changed the hose that goes into the brake booster thinking it was that but it just recently came back. I have changed my ICV over 15k miles ago. I bought a known working AFM on eBay that was really clean 5k miles ago. O2 sensor I changed about 20k miles ago. I have been really busy but last time I pulled my spark plugs two were carbon fouled. Can this be a cause to my problem of surging idle coming and going ? Also I have never changed the TPS and I am always looking for air leaks as I know this can be a main problem to this. I'm just stumped and trying to shoot my shot in the dark honestly. Im not completely worried about the situation because I can still get some good driving in when it idles fine. I just don't want to go blowing money away trying to find it. If anyone had any specific information on what it could possibly be that would be great. thanks

[Lirker]

Bump

[dnguyen1963]

Idle problems can almost be traced to a vacuum leak somewhere. Have a shop perform a smoke test for you.

[7pilot]

The DME is either struggling to compensate for an unmetered air leak, or the Idle control valve is not working reliably.
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