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Thread: car surges when

  1. #1
    Unregistered Guest

    Default car surges when

    car surges when you come to a stop light it drops down in rpm and and than goes back up. What could cause this problem. 94 525i manual. thanks

  2. #2
    Unregistered Guest

    Default

    Check your fault codes....I just had the same problem today......was the O2 sensors......

  3. #3
    Join Date
    Apr 2004
    Location
    Dallas, TX
    Posts
    99

    Default

    I had the same thing in Jan. On mine it was a vacuum hose, but I don't remember which one as my mech. fixed it.
    ...Bill

  4. #4
    Join Date
    Jan 2004
    Location
    Near San Francisco, CA, USA
    Posts
    401

    Default I just went through that with my '90 325is. Step-by-step...

    This could be caused by several different faults. So, first do the stomp test and pull your trouble codes. If you get the oxygen sensor code, you probably need a new sensor. But if you get the LAMBDA (whatever) code, it likely is a vacuum leak. In this case, you need to examine ALL vacuum hoses very critically. Mine was a vacuum hose that was deteriorated ONLY at one end, due to heat. Use a strong light to inspect the hoses. Any hose that is glazed and/or brittle should be replaced. Also the AFM boot should be carefully examined. Be sure your dipstick and oil filler twist-on cover are sealed properly. I pulled my hair out for days because I thought my AFM boot and all hoses were new. Turns out all hoses EXCEPT ONE were new. Finally, when I attempted to remove the hose from the FPR, it would not come off because it was bonded to the nozzle by heat. Pushing down on the hose revealed a cross-sectional split that had been causing an intermittent leak. So a good way to check vacuum hoses is to remove and replace them.


    Quote Originally Posted by Unregistered
    car surges when you come to a stop light it drops down in rpm and and than goes back up. What could cause this problem. 94 525i manual. thanks

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