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  1. #1

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    polaris MSX 150 wont rev over 5800

    hello, first time here, I have a Polaris msx 150 that was running great until a friends son was riding it, they didn't say they rolled it but told me it was down on power, 5800 rpm, without any warning red light,

    I have learned a few of the problems and have looked at all the usually areas ie..oil in the intercooler and map sensors etc, it has a fairly new coolant sensor, I was out testing it the other day and discovered if I unplugged the ose to the wastegate it stumbled a bit at low to mid range and then ran great at high rpms like it used to, I bought a new wastegate solenoid valve thnking that was the problem but it didn't help, any ideas? also I hear ripcuda is the man
    the wastegate arm moves freely, the spark plugs are sooty so I know its running rich, I took the throttle body out and checked for leaks but didn't find
    Last edited by msx150lover; 04-01-2015 at 11:38 AM.


  2. #2

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    polaris msx 150 wont rev over 5800

    I forgot to mention that the wastegate arm moves freely

  3. #3
    ripcuda's Avatar
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    Welcome to GH!

    How many hours on the 150?

    Did all these issues start recently? How recently did it run "properly". Do you recall the max RPM and speed you would see when it ran properly?

    So no red warning lights... no check engine indicators... no other warning indicators? (when you run it up to the 5800ish top speed)

    5800-ish max rpms... sounds like either:
    - boost leak... either tear in hose, hose clamp popped off, leaking BOV
    - stuck open wastegate... would only allow max boost ~6psi... ~5700ish rpms... ~42ish mph (on display)

    Does the ski idle properly? That would rule out intake manifold or ETB boot leak. Possible but unlikely the intercooler could be leaking... usually the hoses or BOV.

    Do you hear a weird honking noise at this 5800-ish top speed? That would be a bad blow off valve (BOV) lifting off it's seat.

    Check the vac/boost source hose that feeds the fuel pressure reg and the BOV. Ensure it's properly connected still.

    If you pulled the hose from the wastegate solenoid to the wastegate actuator...and the ski does NOT overboost (red light, 4800 rpm max limit)... there is something wrong. Sounds like the wastegate itself is somehow not fully closing and allowing enough exhaust bypass the turbine so to not overboost.
    - Did you ever adjust the wastegate actuator arm length?
    - So the wastegate arm moves... but is it snapping back closed pretty tightly (spring pressure from actuator)?

    After all this... perform a compression test on both cylinders. It's possible the Nikasil plating has finally let go in your engine and compression has dropped... and the engine just can't make the power it used to. Does it have a hard time cold starting while *in* the water?

    Post back what you find and we'll keep hunting with you.

    Cheers!

  4. #4

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    all hoses checked out ok, pop off isn't leaking and doesn't make any noises at 5800, ski ran great all morning and then after a short break it wouldn't run past 5800, wastegate moves freely but there is a bit of spring tension, compression #1: 125, #2: 130, I haven't taken the wastegate apart to check to see if its seating properly, the red light does come on after I disconnected the waste gate hose,

  5. #5

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    the ski has 75 hours on it

  6. #6
    ripcuda's Avatar
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    Okay. So you probably are triggering overboost, as you should, when you remove the hose from the wastegate. Ski surges with boost, overboosts, surge is halted, red light flashes, max rpm is 4800. Turn off ski, turn back on. Runs normal again until overboosted again. This is normal behavior.

    If the wastegate snaps shut with good spring pressure, that sounds normal.

    Your wastegate solenoid hangs on a bracket off the valve cover, right? That's the new improved design. Originals were mounted to the side of the turbo and prone to failing. A failing wastegate solenoid usually causes overboost issues... but can fail the other way and only allow min max boost (~6psi). If that happens... no warnings, no lights, and power won't get above ~5700-5800rpms. Does sorta sound like your described condition. Cause when you unplug the wastegate hose you get your full boost back... all the way up to overboosting where the ECU jumps in and reins in the party. We've also seen solenoids only fail under boost. Static testing with 12 volts, they switch fine, but under pressure they stick.

    To recap:
    - your oil is clean/clear... not foamy or milky?
    - your oil level is correct... properly checked?
    - any traces of serious oily mess/gunk in the intake tract hoses, hardpipe, IC, intake? (very slight oil film is normal)
    - no oil slick in coolant jug?
    - turbo shaft not all wobbly and touching compressor housing?
    - engine idles fine even now?

    I'm suspicious of your wastegate solenoid. Ensure it's hooked up right too. You could bypass the hose to the solenoid and connect it directly to the wastegate actuator. This would put full boost to the actuator and force min max boost. If it's the same condition your seeing when it's all hooked up properly... points to the solenoid. If you have a boost gauge, unplug your BOV and plug in your gauge. Take it for a spin. See what you max boost level is when it won't go above 5800rpm.

    Cheers!

    Click image for larger version. 

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  7. #7

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    I installed a new solenoid as that what I thought it might be, I'll try the direct turbo to waste gate hose connection without the solenoid, and I'll recheck for the oil contamination. Would the co sensor or any other sensors produce this condition?

  8. #8
    ripcuda's Avatar
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    Hmmm....

    Now I have in my notes that the ECU will rev limit to 5800 if the MAP sensor readings don't match. Does your 5800 max feel like a rev limiter? Like the ECU is holding you back?

    Double check the wire connectors for the 2 MAPs didn't get crossed. The hardpipe MAP has the 4 wire connector (intake MAP has 3 wires). Pull them and inspect. They gunked with oil? Try swapping them for each other (sensors not connectors) and see if that makes any diff. Often with oil contamination (caused by oil level too high or rollover) the hardpipe MAP air temp sensor (the 4th wire) filament gets damaged. But sometimes the oil doesn't make it all the way to the intake MAP (which has the air temp sensor too, just not used). Thus swapping sometimes can remedy it. But I have to say... there have been multiple folks who had oil ingestion issues that even after cleaning the oil, and new MAP sensors... the ECU just couldn't get past the cached errant sensor data it had when the issue happened. And the ski never ran right until they sent their ECU off to be reflashed back to stock (or upgraded). Hope that's not your issue.

    from my notes:
    Typical problem after a rollover is water and/or oil getting to the boost/temperature sensor and sometimes the MAP sensor (they are both the same component). Once contaminated, these sensors will relay an erratic signal to the ECU and this will trigger a self-protect routine that will put the ECU in limp mode. The limp mode simply means the ECU will set the boost controller solenoid open at all times, which will limit boost to around 6psi, therefore rpm to around 6,000.

    The quick way to solve the problem is to connect the ECU to DW and perform the "clear code" procedure and ..... of course, replace the defective sensor.

    It should be noted that oil and/or water ingestion does not always deteriorate the sensor's internal electronic circuit....... but will always deteriorate the fragile and sensitive membrane that senses pressure. This membrane is exposed to the inside of the intake circuit. Once the membrane is contaminated, the sensor's output values become erratic and/or inaccurate. The sensor can still check ok on an Ohmmeter or a voltmeter, but the signal can be off by a few % points.

    The ECU relies on 2 identical sensors to measure boost and MAP pressure. The algorythm within the ECU always reference the signal of both sensors in relation to a target value at any given throttle (etb) position. If the target value is not achieved..... Bang... the ECU goes in self protect mode....
    With a new solenoid... this is sounding more likely to be your trouble. If you think this might be your issue. I'd be willing to hook up your ECU to my ski and DW (Digital Wrench) and see what error codes there are and clear them. I can't guarantee this will fix it. Some folks need the reflash I mentioned.

    Cheers!

  9. #9

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    that seems to be the issue although I have cleaned them a few times but I never tried to switch them around, maybe its time for a couple of new ones as a last resort, I think then ill be sending you the ecu, thanks ripcuda for all of your input, Ill be getting back to you after I put it back together, thanks again

  10. #10
    ripcuda's Avatar
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    Sure... PM me for ECU assistance. Let us know what you find.

    Cheers!

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