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  1. #1
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    Doylestown, PA, United States
    Member No: 142030 daretowin is an unknown quantity at this point daretowin's Avatar
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    Jun 2006
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    Need help in diagnosing rough idle 1994 530it

    I have had my 530it off the road for teh past 6 years and except for a rough idle she is ready for the road again.

    Here are the symptoms:
    - Engine starts fine, idles up and almost immediately idles down and really rough and sputters. Exhaust smells like she is running very rich. Sometimes it recovers and keeps running other times it stalls
    - Open the throttle and all is good. The engine revs fine and does not miss
    - Drive and all is good until coasting or stopped. Sometimes same as above, but usually keeps running.
    - Disconnect the Mass Air and the idle smooths out and all is good. Reconnect and the rough idle comes back.
    - Check Engine light is on intermittently.
    - Stomp test shows fault code of 1213

    If anyone can provide some suggestions on how to diagnose the cause(s) I would be grateful. Given the cost of some of the possible parts, I would very much prefer to positively diagnose the culprit accurately.

    Lookng forward to your help and advice.

    DaveDave Hollander
    [email protected]
    1994 E34 530it

  2. #2
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    Member No: bonzo's Avatar

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    Re: Need help in diagnosing rough idle 1994 530it

    the code "1213" is an o2 sensor failure. The o2 sensor voltage is read by the ECM which inturn reads the info from the MAS and sets the idle mixture. Sounds like you are on the right track. If the 02 sensor has'nt been replaced by now in your 94, it's time. Also be very careful with the Mass Air Meter. There is a very thin wire (made of tungston) which will heat up to 1100 degrees for 4 seconds every time the engine is shut off - (self cleaning) that literally burns off any contaminating paritcles of dirt, oil etc. for the next start-up. This wire is constantly being measured for "deflection" while the engine is running. Sounds like the MAS is OK. Shop around and you should be able to find a good Boshce 02 sensor for less than 80 bucks. Good luck...

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