Just in the past few weeks my 1993 850 has started idling erratically at start up. At the same time it started idling erratically on bumps. However, generally once it warms up it idles very smooth. I cleaned the battery terminals, the idle air control valve,the flame trap and the throttle body. I also put a can of BG fuel injector cleaner in. Didn't help.

The diagnostic unit showed a bad signal from the throttle position sensor. I cleared it, same problem but no new fault code. Obviously, I suspect that the throttle position sensor is going out. I had similar symptoms 6 years ago and fixed it this way, at the time the car was 6 years old, so maybe I am due. This time though, the car is acting a little different, because last time under pressure the engine surged.

So hear is the question, has anyone ever actually fixed an idle issue by changing the O2 sensor? If so what was the car doing? Is there any maintenance that can be done to an O2 sensor, ie clean it, grease it.

Thanks,