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13 stx15f no power, misfire, need help

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  • 13 stx15f no power, misfire, need help

    2013 stx15f, bought with 135hr, now has 142. Ran great then started missing. Swapped with good used coils and new plugs, started running worse where only run 40-45mph. Took waterbox out and found all corroded so repaired it and new rings and blue boot. Took for test run after sat apart almost a year and ran great. Rode for about 5 min was running 60mph no problem. Went to go out few days later and ran good for about 5 min then started running low power, within 20 min got to running bad with misfire and maybe 35mph. Pulled seat and think misfire on cyl 2 just by pulling wires off to see what cylinders were misfiring but wire wwas arcing so has spark. Few hours later went to ride back to ramp and still poor but got worse and worse, tried taking seat off and all. Got to barely do 15mph then as pulled to ramp would barely stay running. Now i put new iridium plugs, swapped crank sensor & cover for good used one, drained tank, cleaned it out and ethanol free gas. 175psi on all 4 cyl, pulled rail and all 4 injectors seem to all 4 spray good and evenly. Has spark, fuel, compression, new plugs and tried to test run and hard to start. Barely get to fire up and feels like dead throttle. If feather van get to rev up but only could go 15mph and wont get on plane. When on trailer still dead throttle but feather full throttle few times fast and will rev up high rpm. Not strain like in pump. Feels like timing off real bad. All connections look good and clean, all plugs full of diaelectric grease and clean. Also no warning light or codes. Tried holding both buttons for dealer mode but assuming since no flashing light wont swap mode? Has me scratching my head for sure. Thinking maybe tps with desd throttle but wouldnt cause mis at idle even and hard to start. After few tries will start but die as soon as hit throttle unless feather real fast then goto bog then rev up. Only thing i seen is seems like only 38psi fuel but holds even while running and revving so doubt thats any issue especially since ran great at first. When was headed back and ran real bad and barely do 15mph, if i shut ignition off and restart would run faster for a minute then run poor again but no beep or lights. Battery good even after sat year, cranked good and terminals tight and clean. Real clean ski. Storage box has "valves adjusted 118hrs" wrote on it too.

  • #2
    Going to reply in red inline.

    Originally posted by Motojoeis01 View Post
    2013 stx15f, bought with 135hr, now has 142. Ran great then started missing.

    Swapped with good used coils and new plugs, started running worse where only run 40-45mph.

    Took waterbox out and found all corroded so repaired it and new rings and blue boot. Took for test run after sat apart almost a year and ran great. Rode for about 5 min was running 60mph no problem.
    When you repaired the waterbox, did you check the exhaust manifold for corrosion? When the waterbox was repaired, what specifically was fixed and how was it done?

    Went to go out few days later and ran good for about 5 min then started running low power, within 20 min got to running bad with misfire and maybe 35mph. Pulled seat and think misfire on cyl 2 just by pulling wires off to see what cylinders were misfiring but wire was arcing so has spark.
    Did you pull a spark plug when it died? If so, what did it look like?

    Few hours later went to ride back to ramp and still poor but got worse and worse, tried taking seat off and all. Got to barely do 15mph then as pulled to ramp would barely stay running.
    The ski was on the water the whole time or on the trailer?

    Now i put new iridium plugs, swapped crank sensor & cover for good used one, drained tank, cleaned it out and ethanol free gas. 175psi on all 4 cyl, pulled rail and all 4 injectors seem to all 4 spray good and evenly. Has spark, fuel, compression, new plugs and tried to test run and hard to start. Barely get to fire up and feels like dead throttle. If feather can get to rev up but only could go 15mph and wont get on plane.
    Starting on the trailer or on the water? Hot or cold?

    When on trailer still dead throttle but feather full throttle few times fast and will rev up high rpm. Not strain like in pump. Feels like timing off real bad.
    Is this at on a cold start, hot start, or both?

    All connections look good and clean, all plugs full of diaelectric grease and clean. Also no warning light or codes. Tried holding both buttons for dealer mode but assuming since no flashing light wont swap mode? Has me scratching my head for sure.

    Thinking maybe tps with dead throttle but wouldn't cause mis at idle even and hard to start.
    TPS can fail high or low, if the engine thinks it is at higher throttle it will run super rich because the TPS is telling it you are going WOT.

    After few tries will start but die as soon as hit throttle unless feather real fast then goto bog then rev up. Only thing i seen is seems like only 38psi fuel but holds even while running and revving so doubt that's any issue especially since ran great at first. When was headed back and ran real bad and barely do 15mph, if i shut ignition off and restart would run faster for a minute then run poor again but no beep or lights. Battery good even after sat year, cranked good and terminals tight and clean. Real clean ski. Storage box has "valves adjusted 118hrs" wrote on it too.

    Has there been any other recent maintenance done to the ski?
    The pump is okay and not dragging?
    Do you have any crank end play?

    Sean
    The older I get, the more I find myself fixing things that I knew I was doing correctly at the time.‚Äč

    Ski not running well? Check HERE!

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