Odd O2 Behavior

[gte619n]

Fellas,

Question about my 1995 M3. I'm getting a weird Check Engine light coming on intermittently. To start, the car runs great, strong without issue. Occasionally, usually when sitting at a stoplight, the idle will drop from a nice ~800rpm down to ~300rpm, stutter, then completely go back to normal. This throws a Check Engine light.

I read the code from my Peake and I get: FF C9 0D: o2 sensor.

This isn't super surprising, as the car has 170,000 miles and this is the original. So I replaced the 02 sensor... and the issue persists.

Before I go throwing a bunch of parts at this issue, does anyone have any obvious things I should check?

Thanks,

E

[ScotcH]

guessing the O2 sensor code is due to other issues, like fueling or another sensor. Whatever the issue is causes the hiccup (lean, rich, whatever), then DME complains that O2 is not correct reading.

Really a lot of things it could be … quick suggestion: ICV dirty or faulty?

[gte619n]

@ScotcH, ICV is kinda what I was thinking. I can't recall the last time I cleaned it out. The weird thing, is I thought the O2 code threw only after 10 seconds of inconsistent reading. Also, it will clear sometimes after a minute.

[JitteryJoe]

Small vacuum leak causing you to run too lean at low rpm?


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