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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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
Check your fault codes....I just had the same problem today......was the O2 sensors......
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.
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.
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Originally Posted by Unregistered