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  1. #1

    Half boost on msx 150 27 mph only

    hello. i have a msx150 with 50 hrs and i took it out and it wouldnt boost more then half way and only do 21mph. i found the wast gate siezed. i freed it up and now moves very nice open and shut. i took out the map sensors. both top and botton and they are clean with no junk on or in them..i took it back out for a test run did the same thing. check engine came on once and when i shut off and restart check engine whent away and still no power.. how do i reset codes if there is any?please help with this nigtmare what would make it do this...thanks

  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Welcome to GH. Sorry for your Polaris troubles.

    Tell me more about the ski. Is it new to you? You know any history on it? When did it last run right?

    What is the max RPM you are seeing? If the RPMs are being limited by the ECU... that will help us point to the possible issue... since we can't read codes or anything.

    A frozen wastegate gets stuck in the closed position... so you overboost when you go WOT. Did you get that one big surge of power and speed before the ECU tripped overboost, threw a CEL and limited RPMs down?

    Also, do a compression test on each cylinder and report back the #s.

    More questions than advice at this point... gotta pin down the possible issues.


  3. #3
    i had the ski last summer and it flew with no issues. 3200 rpm is all it would give. never gave me the turbo boost at all. so no over boosting. i got it with 40 hrs and it was fine. so last season it was great. can i reset the codes in any way? may be its reading old code due to wastegate being stuck? i will do compression test and report. thank you for your reply

  4. #4
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Hmm... that 3200 rpm limit... sounds mighty close to the common 3400 rpm limit the ECU enforces when the reverse lever is engaged. That is a function of the SIFB (System Interface board)... which is a not uncommon failure item. When the SIFB fails, it's common to have the ECU not allow revs over ~3400 in forward or reverse. Sadly... SIFBs are very hard to come by (OEMs)... and the aftermarket ones currently on sale are very expensive. I'd really try to track one down just to just test your machine before buying if you can.

    Did your ski ever get rolled over? Did you ever have oil ingestion issues previously?

    I've heard of folks having issues with the ECU getting "stuck"... where it can't seem to get past a tripped error code and thus won't ever come out of limp mode. I've read where folks had to have the ECUs reflashed or cleared via Digital Wrench to get them "unstuck". Not sure this is your issue... but could be.

    Do run that compression test... that will rule out a lot of big possible issues. And I'd pop off the hoses... turbo-to-IC, IC-to-intake and even remove the throttle body and examine them closely for anything more than an oil film in them (a film is expected and okay in my experience)... especially in the intake manifold body... a puddle of oil in there would be a sure sign of ingestion issues.

    Also... check your turbo... make sure the impeller spins and smooth.

    Also... make sure you don't cross the wires going to the 2 MAPs... they are identical MAPs with identical wiring plugs... but the one on the hardpipe has 4 wires (it also senses air temps)... while the one on the intake has 3 wires.


  5. #5
    compression is 139 in both cyl. if I took it out with a stuck waste gate it should trick a code right? now if I freed it was I supposed to reset battery? I ran it on hose after resetting battery and I dropped it out of reverse and hit revd hi and it showed boost gauge go all way up? I did not see the wastgate move tho. I broke the waste gate boost sensor so I am waiting on it now

  6. #6
    that was on a hose don't know if it will open up under load

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