Rough Idle

[Will308]

I have a 1991, 525ia, M-50, non vanos. At times the car idles fine, almost smooth as glass. At any engine speed other than idle everything is fine. Then for no apparent reason I get a really rough idle condition. I replaced the idle control valve with a new one under a TSB. It seemed to improve the situation slightly. ( don't get the rough idle as often)
Does anyone have an idea as to what it might be or a permanent fix for this condition. I don't think it's mechanical, since it comes and goes. The dealer's service tech just shrugged his shoulders and said he doesn't understand it since there weren't any fault codes showing up.
Thanks,
Will

[western99]

I have a 1991, 525ia, M-50, non vanos. At times the car idles fine, almost smooth as glass. At any engine speed other than idle everything is fine. Then for no apparent reason I get a really rough idle condition. I replaced the idle control valve with a new one under a TSB. It seemed to improve the situation slightly. ( don't get the rough idle as often)
Does anyone have an idea as to what it might be or a permanent fix for this condition. I don't think it's mechanical, since it comes and goes. The dealer's service tech just shrugged his shoulders and said he doesn't understand it since there weren't any fault codes showing up.
Thanks,
Will