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  1. #1
    Makesumwake's Avatar
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    Diiagnosing rough run engine issue when cold. Im out of ideas....

    BOAT: used 2006 RXT, 160hrs, salt/fresh use

    DESCRIPTION OF ISSUE: when engine is cold: it starts up fine, but runs rough for 4 to 10 seconds then run ok intermittently, then rough again. lacks throttle response and power (top speed is 25-30mph), then will start running fine, then back to a rough idle and no power. acts like it lacks fuel pressure, or like one coil / cylinder isnt working. BUT ONLY WHEN COLD. once the ski is run for about 10minutes, more and more power is gained and the engine runs better and better. after 10min of running it is fine and runs great all day long, even when stopped and restarted after an hour. but let it sit for week, and then the same problem starts all over again.

    Throws no codes / no check engine light

    DIAGNOSTICS SO FAR:
    I have another RXT (2007) and ive swapped over most of the parts to try to find the issue.
    parts tried so far from the 2007 (runs perfect)


    plugs
    coils
    fuel pump/sender assembly
    fuel rail/injectors assembly
    NEW ECU installed already
    idle air control is good
    throttle position sensor works perfect as tested per candoo (gives steady range of proper readings)
    air temp and pressure sensors not been swapped over yet but they do test good with multimeter
    MPEM wires all look good, no signs of rust/corrosion or other issue with MPEM. fuses are all good


    NOTE: i pulled the valve cover off (when attempting to swap the cam sensors between the 2007 and 2006 RXT) and noticed that the plastic cam sensor wheel attached to the camshaft sprocket had fallen off on the 2006. i removed the parts and ordered new parts. however this isnt the issue, as the 4-tec engine will run just fine without the cam sensor even plugged in.

    HOWEVER, the v-ring and thrust washer that hold the plastic cam sensor wheel on have fallen into the engine and are no where to be seen. im wondering if they are somehow down by the crank position sensor and interfering with the operation of the crank sensor. im not familure enough with the internals of the 4tec to know if this is a possibility or not.

    i was going to pull the crank position sensor off but cant get it off due to the retaining bolt being to deformed from rust. but it doesnt backfire, die, or have trouble starting like would be expected from a bad crank position sensor.

    I also have a oil leak somewhere on this 2006 RXT, so it might be time for a motor pull, which i havnt had to do before on any of my skis fortunately, that will be new for me.


    Thoughts?


    thanks,


  2. #2
    waz480's Avatar
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    Have you tried taking the air intake pipe off where it connects to the throttle body and starting the ski and seeing if any water is being blown out of the pipe ? , It could be condensation or split in your intercooler core , Many RXP-X 260 are suffering similar problems to what your are describing and it water thats the problem on them ,
    If you think the v-ring and thrust washer have fallen into your engine i would not start it until you have stripped the motor down and inspected it,
    Just my thoughts and i could be wrong,
    Waz

  3. #3
    mibunkerking's Avatar
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    Failing rectifiers caused problems like that on the two strokes. Might be worth looking into?

  4. #4
    Makesumwake's Avatar
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    its a 2006 RXT, has the old style inter-cooler inside the intake manifold. i took it out and check it for leaks, nothing. no water is inside the intake manifold either.

    i tried replacing the rectifier, it wasn't that either.

    im not sure what to try next.

  5. #5
    HOSS's Avatar
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    Fuel

  6. #6
    HOSS's Avatar
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    Fuel has water in it or idle air control orifice has poo in it.

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