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  1. #1
    GGG's Avatar
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    MSX150 Limiter troubles

    Does anyone know what causes a 2300 rpm rev limit with a check engine light but NO temp light? It doesnt do it until the ski warms up on the hose


  2. #2
    Kosh's Avatar
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    Quote Originally Posted by GGG View Post
    Does anyone know what causes a 2300 rpm rev limit with a check engine light but NO temp light? It doesnt do it until the ski warms up on the hose
    Sounds like exhaust manifold oveheat to me, from memory the temp light does not come on with this input. Not enough water on the hose to keep it cool for extended times.

  3. #3
    GGG's Avatar
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    I dont know. I unplug the sensor and get the same problem, I ground the wire and the temp light comes on and the limit goes down to 1800. Ive changed every sensor on this motor. Im stumped

  4. #4

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    Here is a paragraph lifted from the service manual, page 5.35.

    The limp--home mode occurs whenever a problem is detected as a safety issue in the Electronic Throttle Circuit. The ECU will cut power to the ETB in the event of a PPU, TPS, or wiring failure. When in the limp--home mode, the throttle plate returns to it default, non--power position. This position represents 6% open or approximately 1750 RPM.

    Two things stand out to me. You said you are running it on the hose and the 6% in this paragraph. On the hose this could be 2300.

  5. #5
    Well not to mention they really don't run real well on a hose. Most of the time it's too much pressure( water in the oil) bla bla.. What pronlems are you having on the water. Whats the main complaint?

  6. #6
    GGG's Avatar
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    It is not a ppu, throttle body, tps limp home mode because it responds to throttle. When The ski warms up, the check engine light comes on and it it limited to 2200- 2400 rpm when you hit the throttle. When you let off it develops a miss but I believe that is not the main problem I believe the miss is related to the rev limit because it loses injector pulse intermittently. That limit range seems to be related to exhaust over heat because the coolant overheat is 1800 rpm but the overheat light isnt coming on the gauges and if I short the exhaust temp sensor wire to ground, the limit stays the same but the temp light comes on as well as the check engine.

  7. #7
    What happens in the water? What happens if you start the engine and try to rev in immediately? You have replaced every sensor?

  8. #8

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    Is the manifold hot to the touch when the ECU is limiting rpm? According to the specs the temperature limit is not that high at 60C/140F.

  9. #9
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    Sounds like you have a curly one here. If you are at the stage of wild stabs in the dark, I would suggest disconnecting the O2 sensor. I dont know if it will make any difference or not but it is in use below three to three and a half thoudand RPM, above that it has no control over AFR /idle speed. By disconnecting it it will revert to internal mapping and probably will not settle down on the hose(it will tend to idle higher and take longer to die down after use of the accelerator)

    Have you swapped out the ECU?
    It may pay to unclip the throttle body cover and check for moisture ingress( just be very cautious of the wiper contacts)

    Wouldnt it have been a better PWC if we had the ability to read the dianostic codes!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  10. #10
    Just playin devils advocate. But if it revs when cold then the ecm is responding to something. As far as the o2 sensor, again it would be map-temp related. I'm curious to see if the time-temp is an issue if it every shuts down.. he said he has replaced every sensor, there are ALOT of sensors that play a role in rpm's. I have had ppu's do alot of stupid things, Most of the time with a rev issue it was a faulty turbo. If he would just say how it runs cold On the lake I might be able to tell right off. The ski's really aren't that complicated, We just need a better description from the customer so we can better help diagnose the problem.. ( ;

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