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2000 E39 540 Mixture Control code

Discussion in 'E39 (1997-2003)' started by Marty7, Oct 29, 2009.

    Marty7 guest

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    I just picked up a beautiful 2000 E39 540/6 speed to update my older 540. The car is throwing a code for "mixture control off idle" code 1A and 1B in table OF with my Peake code reader. Beyond that, the car seems down on power overall. I posted a note on another forum and the only suggestion I got was an intake gasket ?

    Any ideas here ? I did notice a very slight anti freeze smell after a long drive yesterday so maybe the intake gasket is the culprit. I have had several 540's but this code is a new 1 on me.. The car also has a slight rattle coming from what I would guess is the timing chain. What is the story on the VANOS unit and what type of a symptom will they give you when on the way out ?
    Any direction would be much appreciated !

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    I don't see any Vanos issues from what you've described. I would however take a close look at the entire cooling system, and plan on replacing the water pump, thermostat, expansion tank and radiator. If you are smelling coolant there's a leak. Look for cracks in the upper corner of the radiator on the drivers side - this is very common and unfortunately it is considered a consumable item. The valley pan is also famous for small undetected coolant leaks that go on for years. If your code reader is indicating a fuel mixture problem do yourself a favor and clean the MAF with a shot of MAF Cleaner and see if that makes the problem go away. Over the years a film can collect on the MAF and compromise its ability to get a good temp reading and this will cause the computer to alter the mixture. The rattle you're hearing is probably a broken spring tensioner - another easy and relatively inexpensive fix. Good luck and tell us how you make out.

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