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  1. #1

    MSX 150 Limited to 3150 rpms - Shut off and restart and its in limp mode upon startup

    Hi all,

    I have a 04 MSX 150 that has a new problem today. Previous owner must have overfilled or rolled machine as I kept getting oil on my sensors causing it to go in limp mode at 4700 rpm's. I just removed the intercooler through the front and cleaned and flushed it at least 30 times until crystal clear water was running out and the fins looked spotless. I installed 2 new sensors and then removed the overflow hose from the oil tank and installed a catch can to prevent oil from getting back into the intact track. Seemed like it was ready to rock as this was the only problem I was having with it.

    New problem today.

    Ran down to the river to try it out as I assumed it was going to run perfect. Started it up and warmed it up, seem to be running great. Gave it the gas took off like new right to 7500 rpm's for about 2-3 blocks and red light started flashing and it went into limp mode. RPM's limited to 3150 this time and it sounded like a tractor. Shut it off and restarted (this usually takes it out of limp until error is caused again). This time when it started it was in limp mode from the get go. Tried several times and it was always in limp mode. Made it back to the trailer and pulled it out of the water. Checked the sensors and there was not a spec of oil on them (nice to see for once). Pulled the main relay while running, and tried restarting. This time no limp mode. Took it back out same thing; idled fine went to give it the gas and it took off for a block or two and back into limp mode. Brought it home started it on the trailer and it was in limp mode. Waited two hours re started it on the trailer with water hooked up and it was not in limp mode and sounded fine.

    What the heck is the deal. Would this be a cold water cooling issue causing the motor to overheat? No temp light showing on dash, only check engine. Water is running out the exhaust and white exit hole by nozzle so it doesn't seem like there is any blockage. I do not have the turbo temp sensor hooked up at the time either. Strange it started happening right after I hooked up the catch can and cleaned everything on the intake track (would that have anything to do with it. It does steam a little out of the top vent filter on the catch can but I assume that is normal).

    Any help would be greatly appreciated. I want to get out and ride.


  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Hmm... sorry for your troubles.

    Did you get the ski with these troubles or did it just start recently?
    When did the ski last run properly?
    I'm wondering if we're still dealing with excess-oil/rollover issues... or if the ski was fixed after those issues.

    I have read that the O2 sensor can be damaged on a rollover... something about it getting water (or was it oil?)... and it giving bad readings to ECU and causing issues. So that's a possibility. Sounds like you replaced the other two MAP sensors already (common victims of excess-oil and/or rollovers)... so should be good there.

    Are your RPMs always limited to 3150 when this happens?
    I'm aware of an overheat rev limit of ~1800... and an overboost rev limit of ~4800... and a reverse rev limit of ~3400. I'm wondering why you're getting 3150.

    Have you checked the wastegate? It's known to seize. You should be able to push the arm downwards (open) about a good inch... and it should spring shut. If it does... it's not seized. This will cause overboost and the ECU will limit revs

    Have you checked the wastegate solenoid? These go bad sometimes and then don't bleed the boost needed to keep the wastegate closed. This will then only allow for about 5-6psi boost and not full revs. You can check this with a 12v source and listen for solenoid to click as it switches the output port (blow through it... you'll see what I mean).

    Cold water shouldn't have any effect on this engine. It's got a separate coolant system with a thermostat to keep it at the needed operating temps. Now if you were overheating... we would investigate this system.

    What happens if you have the exhaust manifold thermo switch (ala turbo temp sensor) hooked up? Same issue? Different rev limit? The ECU uses this switch to detect when exhaust manifold is too hot... and it limits revs to protect. With switch unplugged... you loose this protection... ECU will always think temp is good.

    Good luck!

  3. #3
    Thanks for the reply ripcuda,

    I purchased the ski with 129 hrs and it now has 142 hrs. It has never had the problem I described above until yesterday. As I mentioned above I was constantly having issues with oil contamination so I had to replace several sensors. I decided to remove the intercooler and clean it properly before wasting any more money on sensors. When that issue occurred I could put in new sensors and run it wide open at 68mph on the speedo no problem until the sensors got contaminated and it went into limp mode. After cleaning it I installed the catch can and removed the overflow tube going to the intake to prevent this issue from happening again. I did remove the main harness prior to starting the craft to erase any possible boost errors so I could start fresh. I did read on post (after the fact) that stated this process could wake up old trouble codes so I hope I didn't open a can of worms by doing this.

    Today I went to the river again and had it running on the trailer in the water for 45 minutes running between idle and 5500 rpms. Machine ran great, no warning lamps, no cooling issue, etc. After 45 minutes I decided to open it up to 7500 rpms and sure enough it went into limp mode and the check engine light came on. Again, shut machine off and restarted several times and it remained in limp mode with it running rough and sounding like a tractor and limited to 3150 rpm's. According to the service manual this RPM range occurs when engine cooling issues are present but also states the cooling lamp should be flashing on the dash. The cooling lamp never came on yesterday or today (again it ran great for 45 minutes with rpms ranging from idle to 5500).

    The thing that confuses me is that it remains in limp mode even after shutting it off and restarting it. Usually shutting it off and restarting removes the limp mode until you get on the gas again and it reaches a certain rpm range at which point it triggers it to go back into limp mode. Thats why I thought it was possibly overheating as the machine would sense the temp was too high at startup and keep it in limp mode. I can drizzly water over all parts of the engine including intake and exhaust manifold and nothing sizzles it just beads up and runs off so it does look to be cooling properly. I pulled the engine temp sensor for fun and it began flashing the temp light on the dash so it looks like the indicator does work on the dash.

    I guess I will have to try and find a dealer with Digital Wrench to see what code is being thrown. Its just weird it happened after I removed and cleaned everything. Wondering if it could be a fuel pressure issue as the computer is sensing it is not getting enough gas at wide open. Fuel pump sounds fine though and it runs good as long as you don't goose it. Just tried starting it again after sitting on the trailer for two hours and it stumbled to start and it was still in limp mode but the light wasn't flashing


    Why does it run so rough in limp mode. Is it normal for it to sound like a tractor, run rough, etc? What does the ecu do to cause it to run this way. Does it retard the timing, change fuel map, etc. It just seems like it should limit rpms but continue to run smooth. Just want to make sure this it is normal for it to run rough in limp mode.

    I did notice there is a little oil in the coolant so I suppose this means the head gasket is going to. I checked the compression and it is a little low ( in the low 120s on both cylinders). Manual says 140 +/- 14 so I am a little under the 126 mark but not by much. Inside of cylinders look good (looking through a scope so you can see much). Not sure this is worth fixing at this point as it seems like even if the motor runs perfect the sensors on this machine will just keep making it act up. Wish I could just pull the motor out of my FST and place it in here in the summer and swap it back to the sled in the winter (that would require a little too much effort as they are a pain to pull form both machines). Would be nice to use the snowmobile engine all year long instead of only two months here in MN . The motor in my FST has run flawlessly for the 3 years I have owned it and is the reason why I bought this machine. Figured if it runs great in the sled it must work just as well in the ski, didn't think to check websites like this to see all of the bugs these early Webers had/have.

    Any other ideas on what could be going on would be greatly appreciated,

  4. #4
    O... I forgot to mention all of the turbo/waste gate components are operating properly. You can hear/see the waste gate opening and you can hear the air being expelled when you release the throttle.

  5. #5
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Not sure about the rough running. I've not read that problem from others. Always seems the ECU limiting revs like a limp mode is just that... stopping the rev but not running any worse. Could be a head gasket like you said. Which could also cause your lower than avg compression results.

    I have these notes about coolant/oil mixing:
    There are a few possibilities:

    1-) Water pump seal. If the seal is damaged, coolant will flow directly into the the crankcase.
    2-) Turbocharger cartridge housing. This is cooled by closed circuit coolant. If the turbo watercooled housing is cracked, coolant will make its way into the crankcase.
    3-) Oil cooler leak. Closed circuit coolant is used in this cooler. A leaking passage is possible. However, because oil pressure is greater than coolant pressure, it is much more typical to see oil in coolant than the opposite.
    4-) Leaking head gasket. At a minimum, take a compression test.
    5-) Cracked engine block. This would leak even with the engine not running.
    What was the deal with the exhaust manifold (turbo) thermo switch? (rear side of exhaust manifold) Is it plugged in or not? If so, could cause overheating rev limit... if unplugged... then it can't and ECU thinks all is good.

    Hope someone else chimes in some ideas too.
    Good luck!

  6. #6
    Sounds like it will be fun to isolate the coolant/oil contamination point, there are quite a few places to look. In regards to the turbo thermo switch I currently have it unplugged so I can rule out that as a cause while I try and figure out everything else. When I bought the ski I found the sensor disconnect so I plugged it back in and it would go into limp mode with a max rpm of 1850 rpm. Replaced sensor and it worked fine from then on. I am just going to leave it unplugged for now so it dosn't cause me any other issues. If I get this new problem sorted out I can plug it back in for added protection later.

    I'm kinda concerned about the rough engine when in limp mode. I was under the assumption that all of these MSXs would run rough whenever they went into limp mode (limited to below 3000 rpms). When I had the sensor contamination issue you could run it to just shy of 4700 rpm's all day long and as soon as you hit 4700rpm' s it would go into limp mode and run rough. If you shut it off it would return to running normal until you hit 4700 rpm's and then go back into limp mode with a rough engine sound and be limited to 2XXX rpm's. One time i had an intake hose come off of the intercooler and it went into a limited 5000rpm limp mode and the engine remained running smooth, it was just limited to 5000rpm as the computer detected inadequate boost. Maybe when the engine detects something serious and the rpm's are limited to either 1800, 2200, or 3000 it does something to make it run rougher to save the engine. Curious if anyone else has experienced this rough sounding engine when in limp mode and rpm's are limited to 1800, 2200, or 3000.


  7. #7

    I ended up taking it to a guy that specializes on working on Polaris vehicles. The Polaris dealer didn't even know where to hook up digital wrench to the MSX so I figured I wouldn't waste any money bringing it there as I probably knew more than them. He hooked it up to digital wrench and figured out it had a spark issue even though it had spark at idle when pulling the plug and looking at it. It turned out to be an almost broken wire going to the PTO coil (broke way down in there and basically was undetectable unless you knew what you were looking for). It had nothing to do with overheating which is why I never saw an engine temp light. It looks like it just was limited to 3,150 rpm’s because it was running on one cylinder. At first they thought it was the computer but luckily found the broken wire. It looks like the wire was only holding on by one little strand of wire and when you got on the gas it wouldn't allow enough current through to allow for the proper spark so it was kicking into limp mode. Sometimes when you started it it was only running on one cylinder which explains why it sounded so rough. Shop wasn't to concerned about the oil in the coolant as it was so minimal and said it was not losing any coolant so it shouldn't be a head gasket issue. It was a cheap fix so I'm excited about that. It will be nice to try the catch can setup to see if the machine continues to run well now that the intercooler has been thoroughly cleaned and the oil vent tube has been rerouted from the turbo intake to the catch can to prevent any future sensor contamination from oil.

    Fingers crossed, I might actually get to enjoy the rest of the summer on the water.

  8. #8
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Great news! Thanks for the update. Nice to hear the fixes to problems. Helps us all.

    Man... a frayed wire deep in the loom... *shudders*... that would be such a hassle and nightmare to find. Awesome you found it.


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