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  1. #1

    What could cause a BIG surge at idle?

    2005 RXT with a fresh rebuild. Ran in on the host last night to check the coolant. It starts up and idles at 2100 +/- RPM but then after a bit it would drop RPMs like it was ready to die (sounded like a cold engine when you remove the choke) and would go down to about 1000RPMs and then jump back up. If I hit the throttle it would bouce back up immediately also. I know surging is common and no problem, but this seems excessive.

    Thanks,
    Greg


  2. #2
    Huh? Dyoung's Avatar
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    I'm not saying that this is your problem but it's could be a timing issue. I had the exact same symptoms after reinstalling my head after an overheat. We basically just took it it apart and repeated all of the steps to time it correctly and that fixed my problem. hope this helps....


    edit:I know you haven't had it on the water yet but my ski was down 700-800 rpms on top as well


    Quote Originally Posted by ghlenz View Post
    2005 RXT with a fresh rebuild. Ran in on the host last night to check the coolant. It starts up and idles at 2100 +/- RPM but then after a bit it would drop RPMs like it was ready to die (sounded like a cold engine when you remove the choke) and would go down to about 1000RPMs and then jump back up. If I hit the throttle it would bouce back up immediately also. I know surging is common and no problem, but this seems excessive.

    Thanks,
    Greg

  3. #3
    Site Admin Green Hulk's Avatar
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    Vacuum leak

  4. #4
    imp0ster's Avatar
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    Quote Originally Posted by Green Hulk View Post
    Vacuum leak
    yup or misinformed MAP

  5. #5
    Quote Originally Posted by Green Hulk View Post
    Vacuum leak
    I could buy this as an option - as it sorta acts like an old car with a vacuum leak - expect that it corrects itself and idles back up. I thought a vacuum leak caused a high idle condtion? When you guys say a vacuum leak, do you mean that it is sucking air - this which would attribute to a high idle which I do not see as my issue. Do these engines use vacuum to run correctly like an old carbed car engine?

    Where is a logical place that this could be leaking.

  6. #6
    Quote Originally Posted by imp0ster View Post
    yup or misinformed MAP
    What is a "Misinformed MAP"? - a bad sensor providing bad information?

  7. #7
    rangermtb5's Avatar
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    Quote Originally Posted by ghlenz View Post
    I could buy this as an option - as it sorta acts like an old car with a vacuum leak - expect that it corrects itself and idles back up. I thought a vacuum leak caused a high idle condtion? When you guys say a vacuum leak, do you mean that it is sucking air - this which would attribute to a high idle which I do not see as my issue. Do these engines use vacuum to run correctly like an old carbed car engine?

    Where is a logical place that this could be leaking.
    Check the pipes from from the SC to intake mani (if stock) or the pipes from SC to IC to intake mani (if running after market IC). If the clamps aren't tight, could be leaking air.

    are they new spark plugs?

  8. #8
    Quote Originally Posted by rangermtb5 View Post
    Check the pipes from from the SC to intake mani (if stock) or the pipes from SC to IC to intake mani (if running after market IC). If the clamps aren't tight, could be leaking air.

    are they new spark plugs?
    Piping (stock)/Clamps are tight and the plugs are new.

  9. #9
    BTW - another piece of information. I am running an XCharger with stock injectors. Could this cause the issue? Does the XCharger produce more boost at idle?

  10. #10
    Eric Ocman's Avatar
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    Quote Originally Posted by ghlenz View Post
    BTW - another piece of information. I am running an XCharger with stock injectors. Could this cause the issue? Does the XCharger produce more boost at idle?
    No boost at idle. Did you install anything else besides the charger and injectors?

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