Idle issue...

[FreedS4]

I can't seem to pin point exactly what is causing my idle issue. I've got a 89 325i, with an M30 AFM and 19 lb injectors (had them, with no issues for 6 months). About a month ago, the car started having an issue with idling at an exact RPM, that is to say that it would surge up and down every few seconds, but wouldn't stay put at one RPM. Now, at start up, the car revs up to nearly 2000 RPM and then drops back to 1100 or so until it gets warm, then does the surging thing from around 700-900 RPM. A few oddities are that when I let off the gas with the car in gear, sometimes the RPMs don't want to drop below 1100 or so, in essence keeping momentum in the car and it will start to buck a little. The RPMs drop back to 700-900 as soon as I push the clutch in and take it out of gear. Also, when I turn the AC on, the RPMs shoot up to over 1250 and stay there the entire time the AC is on. I've replaced the vaccum lines, rotor and cap, adjusted the valves, and got a different AFM to no avail. I've searched but can't find anything that has helped yet. Any ideas what's going on or how I could fix it? Thanks in advance.

Chris

[bmw325csi]

idle control valve is a likely culprit

[ben312]

Idle control or there is a leak somewhere that you are unaware of. Check all the hoses all the way back and then check whatever they connect to, a leak somewhere else could in turn cause a vac leak. Example: a whole in the valve cover could cause loss of pressure in the breather, or a hole in the charcoal evaporater could cause a loss of pressure into the throttle body. check you control valve first tho

[FreedS4]

Check the ICV via the instructions in the Bentley? Or is there some other technique I should use?

[ben312]

I would start with what the bentley says. If that still does not solve the problem then look for anything that could cause a vac leak. If your sure there is no vac leak try tuning you idle control a bit.

[nickpdx]

Yup, ICV or vac leak. Try cleaning out your ICV by removing it from the car and thoroughly spraying out the inside with carb cleaner until black crud stops coming out if it's dirty, which it likely is. Usually only a temporary fix but it might pinpoint the issue as your ICV.