I have a 90 535ia w/ 213k. All was well when it started to idle erratically, after engine is hot, now even after a cold start. The O2 sensor has been replaced 2x and the CHECK ENGINE LIGHT goes on when this is happening. It was happening with the stock chip, now I have a Jim C and still does it. (yes 92 octane) The gas pedal diagnostics gave me a 1222 code and the chart says Lambda Control #1.
Could it be a vaccuum leak or an idle valve? The mechanic says it could be the computer (yikes!).
Any input will help.
Thanks and Happy New Year!