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    Hesitation during acceleration

    Hey guys, I have an m50 swap with m3 cams and been having some odd problems lately. And I searched but couldn't find anything similar to my exact problem.

    I got the alternator replaced a few weeks ago and when I got it back from the shop the idle would surge from 1k to 2k. I didn't think anything of it cause it would do it after the battery was unplugged but it would go away after a 15 minute drive or so. I expected it to go away but it didn't stop for a week. After it went away everything was fine until last Friday. I was driving to a friends house when all the sudden the car hesitated when I was accelerating and then it wouldn't idle at all. The RPMs would go up between shifts and when i rolled up to a stop light it would idle at 2k then sometimes raise up to 3k. I would have to drag the motor down by putting it in gear just so I wouldn't like an asshole at stoplights. I probably burned my clutch up by doing that but fuck.

    I didn't drive the car for a few days after that until I took it to Rob at e30 Motorwerks yesterday. On the way there it didnt do it all which pissed me off cause I wanted him to see what was going on. We both checked it out, we couldn't find any vacuum leaks of any sort, or any problem for that matter. He gave me an AFM he had laying around and it calmed it down a little bit. But today I was driving and I was accelerating, not WOT but giving it some juice and then it hesitated a few times again. So I turned around and took my sisters car to where I was going.

    Also the car has done this since I've gotten it but when I start it up it idles fine at around 700-800 RPMs but once I start driving and roll up to stop lights it stays at 1000 or 1200 RPMs. I haven't been able to figure it out.

    What do you think is going on with this hesitation, fuel regulator? Sticking Vanos?
    Last edited by lga714; 03-11-2010, 12:53 AM. Reason: Hit enter before I finished

    mtechII 5 lug S50

    #2
    I would check the fuel filter and make sure the in tank pump works.
    If that end is good, you may have to test the crank position sensor.

    m

    Comment


      #3
      Thanks, would the fuel filter and tank pump also be causing my relatively high idle problem I mentioned since owning the car? It's always at 1000 or 1200rpm. I'd like to get that down to 700 or 800rpms.

      mtechII 5 lug S50

      Comment


        #4
        Normally the idle is unaffected by the lack of fuel because there is no demand for more volume. Under load, yes.
        Your tech says there are no air leaks, but I would keep looking for one.
        Also make sure that the throttle cable is not too tight and the cable is not sticking.
        Make sure that the Throttlebody butterfly is not sticking just off idle or closed position.

        m

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