for some reason my post is being rejected. this is my third and final attempt my M now has 35k miles. it ran fine on a recent trip (150+ on the gps) but then developed a strange 600 to 1400 surge at idle (intermittent). here is what i did: 1. drained some coolant and removed expansion tank 2. removed all inlet air components 3. replaced 2 idle control units, bosch 0280140505 4. cleaned every electrical cable connection in sight. reconnected with silicon grease on contact block 5. cleaned hot wire meters with CRC Mass ASir Flow spray cleaner. car now does not surge but idle is not perfect. 7/12 check engine light stays on. code is 1211 which is lambda regulation. thinking about replacing the oxygen sensors.
Have no clue why nobody is answering; have the idea there are not so many 512TR/M guy's available ! Replace the Laqmbda sensors / O2 sensores. Normally should they be exchanged at 70.000 kms ... Hopefully your problem goes away... I have had similar electrical trouble; one of it was replacing the two (blue) water temp sensors... (cost € 10 each...) and that helped. In my 512TR I had lots of trouble with the the SlowDown lights... new Bosch O2 sensors are ordered... Next weeks the Lambdas will be changed... Keep us informed or mail me with [email protected] !
Silicone vapors in the smallest amounts will contaminate/destroy an oxygen sensor. Even the vapors from silicone sealants will damage a sensor. Look at the latest RTV sealants, and you will see that some of them are labeled "oxygen sensor safe" I would not use any silicone spray lubricants or greases in the engine compartment of a modern car with oxygen sensors, you are are just asking for trouble if you do.
