car idles like a rotary

[Yonkers320is]

have a 91 325i and it idles like a rotary (as in the sound), it doesn't shut down or anything, and there is a small vibration. The check engine would light up, but goes out with a blip of the throttle, until the car stays idling again.
Changed plugs, cap, rotor. maybe bad ICV?

[jlevie]

The CEL coming on when the engine idles and going off with a throttle blip is either a bad O2 sensor or intake leaks. Or both. The lifetime of an O2 sensor is not more than 100k, so if that applies to the car replace the sensor. Then have a smoke test run to find the intake leaks.

[Yonkers320is]

thanks, will do that

[crazyman]

usually if the intake has a leak it has a high pitch whistle, the easiest way to check that is take a can of WD40 and spray all over and around the intake gaskets. if the idle jumps when you hit a certain spot then there's your leaky spot. As far as the o2 sensor the only thing you can do with those is just replace it and see what happens after you do.