E36 325i Idle Problems

[wsiemens@xxxxxxxxxxxxx (Wendall Siemens)]

Someone must have seen this one before!

	My 92 325i does not idle properly. It will sit around 800 RPM and then
start bouncing from almost stalling (300) to 1500 RPM. The car has a K&N
core filter and aftermarket exhaust cat back.
What I've found out:
	If I disconnect the Throttle position sensor, it appears to idle normally.
	If I remove the K&N filter, it will oscillate, but not near as severely.
(600 - 1000RPM)
	My check engine light is on and off during normal driving. I tried about
fifty times to get the motronic to tell me what was wrong but no luck.

Questions:
1 How does the throttle position sensor work, and is mine screwed?( It seems
to act like a potentiometer varying from 20 to 50 ohms)
2 If this isn't the throttle position sensor what could it be?
3 Last but not least, would and after market chip (Jim C) help cure the
problem if it is caused by the lack of back pressure?

Thanks,
Wendall
92 325i E36 on a roller coaster ride

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