car surges when

[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

[Unregistered]

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

[DallasBill]

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.

[Warren N.CA]

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.



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