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  1. #1

    Join Date
    Feb 2008
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    No. MN
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    320

    MSX 150 Hunting at Idle - Max RPM at 5700-6000 - Using 'Lots" of Gas

    I read up on possibe problems. Lowered my oil level. Opened up inetercooler and cleaned. Took entire intake off and cleaned. Oil in both spots. Replaced both sensors. Still does the same thing as it did before. Hunts at idle. It will go up to 5700 fine. Then dog out as you go to full throttle. If you blip the throttle, it will go to 6006-6200, then tail off again. Almost seems like it is dropping a clyinder. What is warm engine compresson supposed to be? How long to I disconnect the ECU to get it to re-sweep the ETB? I cannot find the procudure for checking/re-setting the PPU. Anybody have that?

    While I had it open, I installed the 167 degree thermostat and put in the new colder NGk plugs. I have done all that I have read about. All hoses are good and tight. No code errors currently. I did have an overheat, but intake screen was plugged. That is fixed.

    I think the hunting idle and no top RPM are related to the very high usage of gas. All comments and suggestions welcome. i did put one of the two sensors in just before I cleaned all the oil out. Maybe I toasted it. The other is brand new. I will swap the lower one with the upper and see. I will clean up the older 2 and re-try those as well. Dam there is alot of sensors on this machine.


  2. #2
    pimpdaddy1787's Avatar
    Join Date
    Aug 2009
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    southern maryland
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    59
    i aint the smartest man but kinda sounds like u have a vacuum leak? i work on cars for a livin and tinker with ski's more and more. juss my $.02

  3. #3

    Join Date
    Feb 2008
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    No. MN
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    Took out again and switched MAP sensors. Idled OK at 1st, then it was bogging on take-off, but after a few minutes it like picked up another 800 rpm and went to 6800 rpm. Then after a few more minutes it dropped off back to 5700-6000. Slow to idle and it is hunting. Almost was like it was missing, but not.
    Checked plugs. They are black. Checked compression again and it is 120 warm. Think the digital wrench has/will pick up this problem? No codes, no lights.

  4. #4

    Join Date
    Feb 2008
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    No. MN
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    320
    Anybody want to buy it? $3,250 with the cover.

  5. #5

    Join Date
    Apr 2010
    Location
    Stamford CT
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    129
    "No code/no lights". Have you confirmed that there is no boost leak? I would check intake hose clamps, bov, wastegate hoses, bov hoses and the isolater gasket under the throttle body (check last). Check everything from the turbo outlet to the intake manifold gasket for leaks. Often, hose clamps loosen and/or the isolator gasket developes a leak.

    The trick I use to see if the intake system is tight is to gently pinch the wastegate actuator hose (right next to the actuator located on the exhaust manifold) with a pair of visegrips or similiar. Then take ski for a ride. From a standing start, I slowly (very, very slowly) apply throttle. If the ski reaches max rpm or trips the check engine light (an over-boost situation, rpms limited to around 4700 w/ light, but clears on restart) then the intake is "boost tight". By pinching the hose, you take control of turbo from the ECU and isolate the intake tract from turbo outlet to intake manifold gasket.

    If the ski never reaches max rpm or triggers an overboost condition with this test then there is a boost leak that needs to be located and corrected before worring about any other component on the ski. Even if everything else is 100%, boost will not make it into the motor.

    If you reach max rpm, then the intake system is sound and then there are a few possiblities:
    1. one(two) of the two intake system sensors is faulty
    2. the wastegate solenold control circuit has a fault
    3. ECU is buggy and needs a reset
    4. the turbo itself could be damaged

  6. #6

    Join Date
    Feb 2008
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    No. MN
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    320
    Not sure I follow. Under both screnerio's the ski can limit RPM with an overboost, so how can you ever get to max. rpm? Are you saying it will get to max. RPM if you go slooowwwly to full throttle. If too fast the light flashs and you need to re-set and try again? I had the entire intake tract off. From the turbo outlet to the intake ports of the cylinders. There are only 3 hoses. the elbow off the turbo and 2 couplers for the ETB and intercooler. Cleaned and looked over all three and they looked good. I Saw the isolater gasket, but did not remove as it looked intact and seated on the intake. Think you can spray starting fluid around the hoses/sealing flanges to see if the engine RPM picks up?

    How do you reset the ECU? Mine has been unplugged off the rlay for 2 days and I unplugged it with the ECU awake.
    How do you calibrate the PPU?

    When I bought it it ran erratically to 7400-7800 and felt like it was hitting the rev limiter. Cleaned the MAP's with starting fluid and canned air (that is when I saw some oil) and has been this way ever since. Hunted at idle, but it ran. I think I have gas in my oil because of all the gas ity has been consuming. Think that could have something to do with it? I am only running this thing 10 minutes at a time, so do not want to spend money on an oil change until the dam thing runs right.

    I have another MAP coimg tomorrow, so we'll put that one right into the bottom of the intake so as to remove that from the equation. I will rotate my other two into the top position and see if the problem clears.

    Anybody else have some input?

  7. #7
    desperado's Avatar
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    Aug 2007
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    Montreal, Canada
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    I suspect your MAP sensor is bad. These are the usual symptoms.

  8. #8

    Join Date
    Apr 2010
    Location
    Stamford CT
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    129
    Your starting fluid comments got me thinking and I thought I would share a pair of pictures. Something to consider if replacing the map still doesn't correct the problem. It is probably safe to say that at idle on the trailer and at idle in the water places two different loads on the engine, but normally the ECU manages to find the same idle speed around 1500 +/- 50. So the ECU must be controlling the throttle to achieve this, actively. If there was a leak below the throttle body, either the isolator gasket, its clamp or the sealing surface between the throttle body and the gasket, then the ECU would have a difficult time finding idle. Moving the throttle would have no effect on the air going through the leak.

    These pictures are of the leaking isolator gasket on my MSX 150. With some help from here and a bit of luck I was able to find it in about an hour. I was limited to 6000rpm with no light however, I never ran it enough in this condition to observe the erratic idle you describe.

    Can you see the hole?

    Click image for larger version. 

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    How about now?

    Click image for larger version. 

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    I was ready to put this back in the ski. As I drying it off after cleaning it, that is when I found the hole. Once replaced, the ski was once again 100%

  9. #9

    Join Date
    Feb 2008
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    No. MN
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    320
    Where the heck does that go? I took my ETB off and mine looks just like a thick rubber gasket that sits on top of the intake. Does the bell extension go up or down?

  10. #10

    Join Date
    Apr 2010
    Location
    Stamford CT
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    129
    It is upside down in the pictures. Bell points down and is clamped to the intake manifold with a hose clamp. The four bolt flange is where the ETB mounts.

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