Floyd Rogers wrote:
> "Fred W" > wrote
>
>>bmwguy2 wrote:
>
>
>>>My car's idle is not stable (it fluctuates b/w 800-1800 RPM) and I was
>>>told to replace the O2 sensor and it might fix the problem
>>>
>>
>>It might, but there's a whole better chance that it won't. When O2
>>sensors go bad they throw check-engine codes and the car idles very
>>poorly, but genrally not where the idle races up and down. Your symptom
>>sounds a lot more like a severe vacuum leak. Look around in the ngine
>>compartment for a hose that has blow off or cracked or a cracked rubber
>>intake manifold boot.
>
>
> Well, Fred, it's not likely to "throw codes" on a pre-OBD car. ;->
> However, I agree about the vacuum leak. Ensure that the oil
> filler cap and oil dipstick are firmly seated, too.
>
> FloydR
>
>

Are you saying the ECU will not generate a check engine light on a 1986
325es if the O2 sensor has gone tits up?

Even the earliest Motronic ECU will show an O2 fault via the check
engine light.

http://www.unofficialbmw.com/repair_faqs/motronic.html

--
-Fred W