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Increasing the idle rpm

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    Increasing the idle rpm

    I have an M40B18 that recently got a 90amp alternator attached because the original 65amp is no longer being made. It is idling a little rough not bad like it is going to stall it is just having a little trouble idling low and still spinning the alternator. Is there a way to raise the idle up about 250rpm without having the ecu kick it back down?

    #2
    Idle speed is not adjustable.

    if it's not idling nice, you could have a vacuum leak, dirty injectors, misadjusted TPS, sticky ICV, etc. Even with the extra load of the alternator, it should still idle at the target idle speed of approximately 650-700rpm.
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    Bimmerlabs

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      #3
      Yeah you probably have a vacuum leak. I have one right now lol. Try cleaning out your ICV with carb cleaner, if it doesn't help then you have a vacuum leak.
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        #4
        Thanks guys. I will give that a try and see what happens.

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          #5
          The alternator won't put more load on the engine unless you are drawing more amps. I.E. - The amperage rating is a max capable rating, not a constant output. Current is always drawn from a source, not pushed from it.

          In short, you have another problem unrelated to the alternator.

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            #6
            Yeah it came stock with a 65 amp and now it has a 90 amp.

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