Idle issues?

[ryan.ororke]

I have a daily driver 325e, everything in the engine is stock. Just as i got home from work today, my idle became very rough (at a stop) dropping from 1100 rpm down to roughly 8-900 rpm, then bouncing back up again and repeating for about a minute before it sorts itself out and settles at a warm idle of 1100.

I just barely tapped the throttle to see if it would do it again, and it did, just for about ten seconds. Had my dad take a look, he says it acts like a vacuum leak, but those are constant, whereas this is just temperamental really. Ideas? I know old cars need constant care sometimes, but i wouldnt have a clue where to start on this issue.

[jlevie]

Start with a new O2 sensor, valve adjustment, cleaning of the ICV, new plugs (NGK ZGR5A), new ignition wires and distributor. Also check to make sure that the idle switch in the TPS is working. Then have a shop run a smoke test and fix the leaks it reveals.

[603Racing]

1100 rpm at idle seems a bit high, but that may just be my old muscle car roots lurking around.

[gaineyz]

I've had a similar problem on my 87 325es for the past year. The list jlevie gave is a very good place to start. I'll also add that the valve cover gasket and oil cap can cause vacuum leaks as well. I have as yet not found the problem with mine (despite having changed all the the vacuum hoses) and have to tolerate the 1100-800 rev/drop/rev/drop cycle every time the car idles once it's warm. Doesn't do it cold.
Good luck and be sure to let us know what fixes your issue.

[ryan.ororke]

Well lack of money stops me from doing anything immediately, but I will post when I find any problems. As of now though it only has the issue when I trick it into doing so.

[jlevie]

I've had a similar problem on my 87 325es for the past year. The list jlevie gave is a very good place to start. I'll also add that the valve cover gasket and oil cap can cause vacuum leaks as well. I have as yet not found the problem with mine (despite having changed all the the vacuum hoses) and have to tolerate the 1100-800 rev/drop/rev/drop cycle every time the car idles once it's warm. Doesn't do it cold.
Good luck and be sure to let us know what fixes your issue.

Have a smoke test run. There are a number of places to have an intake leak.

[ST1G]

1100 rpm at idle seems a bit high, but that may just be my old muscle car roots lurking around.

Mine doesn't idle that high. seems a few hundred too high to me.