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  1. #1
    thompsdw's Avatar
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    Rough Idle NA MR-1 Engine

    I have a couple of skis with MR-1 engines that are naturally aspirated engines installed. I have had problems with a rough idle on one of the skis since I purchased it and the dealer was no help. I did check the coils per the service manual and didn't find any issues. Here is another interesting fact that I found out recently. I was wondering if someone could better pinpoint the trouble based on this symptom.

    Ok - so I know this isn't how I normally should do it - but we were thinking safety. Due to some medical issues with my Daughter, I didn't get around to changing the oil in either PWC until a couple days ago. It was a balmy 38 degrees F outside, so my son and I opened all 3 garage doors and pushed the ski 1/4 way out of the garage (but not completely so it would be somewhat warm when changing the oil). We put a digital CO monitor in the garage and fans to clear the air after the engines ran for ~10 minutes to warm the oil. We started the engine and went outside where we could monitor the CO levels safely.

    Here is the interesting fact - on the ski with the rough idle engine the CO level was more than double (~520 ppm) than the smooth idle engine (~180 ppm). So, I am assuming that the likely causes are still injectors or coil packs, right? Anything that can lead to incomplete combustion and produce more CO? Any other ideas??


  2. #2
    Boilerman Bill BPnta's Avatar
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    Put new plugs in, right? I'm sure you have already but just throwing it out there.

    When I had my VX new plugs solved the rough idle issue.

  3. #3
    Kaybat's Avatar
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    plugs.
    I have 2 of those motors in my jetboat,and they're notorious for fouling plugs....especially if you're not wot alot of the time. I actually went one heat range hotter(my local dealer recommended it) and haven't fouled a plug in a year....bulletproof motor(loud as hell though!!)
    good luck

  4. #4
    thompsdw's Avatar
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    Great suggestions, but one of the first things I tried was to upgrade to the iridium plugs on both skis. Changed the stock resistor plugs before that with no real change in symptoms. Given that I can check the COPs via the manual, I am leaning to the injector spray pattern. BTW - I did swap COPs with the other ski to see if the problem moved and it did not.

    Is there anything else other than the injectors that could cause this?

  5. #5
    Kosh's Avatar
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    Back to basics, check the fuel pressure, I am not familiar with your model but if you suspect a rich mixture I would be checking to see if the regulator is doing its job. A pain to connect up though.

  6. #6
    fx160's Avatar
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    try reading the co level on both at just above idle
    as i think it may just be the balance of the throtle bodies
    have a look at the buterfly's on both skis and see if there aligned diferently

    kev

  7. #7
    thompsdw's Avatar
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    Quote Originally Posted by Kosh View Post
    Back to basics, check the fuel pressure, I am not familiar with your model but if you suspect a rich mixture I would be checking to see if the regulator is doing its job. A pain to connect up though.
    Great idea. I will get a pressure gauge installed and check to see if the pressure is within specs. I would think; however, that it would run very poorly if the pressure at all injectors was below the spec. This engine will run, just the idle and engine vibration seem off at times. Thanks for the idea.

  8. #8
    thompsdw's Avatar
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    Quote Originally Posted by fx160 View Post
    as i think it may just be the balance of the throtle bodies have a look at the buterfly's on both skis and see if there aligned diferently
    Another good idea to check. Thanks guys.

  9. #9
    volltrex's Avatar
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    tompsdw..

    What model do you have? this is important as there are differant MR-1 set ups.
    If a HO, then check all bypass motor connections......they can come loose, if one is off then this will cause a rough idle.

  10. #10
    thompsdw's Avatar
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    The motor is a Non-HO motor. Single throttle body.

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