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  1. #1
    outnumbered's Avatar
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    Diagnose issue on 2017 SVHO

    I discovered yesterday that there is another forum member that is having the exact same issue that I am having.

    1. We both have an FX SVHO. Mine is a 2017, he has a 2016
    2. We both recently replaced the shortblock
    3. We basically have the same mods (Stage 3 with 17lb wheel)
    4. Both ski's run fine until we go full throttle. It then loses power.
    5. The ski does not completely shut off, but it does run roughly, almost like it is running on 3 cylinders.
    6. Here's the "head scratcher", once the ski cools down, it runs fine.
    7. There are no alarms nor codes--nothing.
    8. There does not appear to be any boost leaks. The ski has no issue making boost. The clutch is fine.
    9. It does not appear to be an exhaust leak, as my ski is pulling 100% of it's air from outside the ski.
    10. Air/fuel numbers are fine.
    11. It does not appear to be the plugs. If one wasn't firing, it would look fouled. Again, the ski run's fine during normal operation.
    12. The other forum member has replaced plugs and coils with no change.
    13. I have changed tunes with no change.

    So the question becomes, what component on the ski would cause it to fall on it's face in the upper rpm's, and run roughly until it sits for a while, without throwing a code or sounding an alarm? Would a dealership with their diagnostic tool be able to run the issue down without the ski throwing a code?

    $200 for anyone that can diagnose this!
    Last edited by outnumbered; 09-21-2019 at 07:15 AM.

  2. #2
    outnumbered's Avatar
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    The service manual mentions voltage and continuity of the ETV system. Could either of those affect the ski at WOT more so than normal throttle without throwing a code?

    Again, I think the clue here is that it run's roughly until it cools down. So that would not appear to be an electrical issue.


  3. #3

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    Since it sounds like a heat related issue, I'd suspect it's a lack of cooling causing a hot spot in one or more cylinders causing detonation until it cools back down.
    Could be caused by a coolant mod such as running an additional coolant inlet line through to the anode under the intake, which messes up the flow through the water jacket in some cases.

    This is based on having ruled out exhaust leaks, having correct AFR's and ignition coils being OK along with no fouled plugs. I don't think it would be ETV related as that would either throw codes or AFR.

    Hope that helps!

  4. #4
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    Quote Originally Posted by ryllz View Post
    Since it sounds like a heat related issue, I'd suspect it's a lack of cooling causing a hot spot in one or more cylinders causing detonation until it cools back down.
    Could be caused by a coolant mod such as running an additional coolant inlet line through to the anode under the intake, which messes up the flow through the water jacket in some cases.

    This is based on having ruled out exhaust leaks, having correct AFR's and ignition coils being OK along with no fouled plugs. I don't think it would be ETV related as that would either throw codes or AFR.

    Hope that helps!
    What complicates things is that I haven't changed anything on the cooling lines that was any different prior to replacing the shortblock. The other forum member has the exact same routing. I do have the full Riva Pro series cooling system sitting here waiting to be installed just to see if that makes any difference. But again, if my cooling line routing wasn't a problem before, why would it be a problem now?

  5. #5

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    What was the reason for the shortblock being replaced? If the setup was working great before and that was the only thing that's changed, then I guess your options are to either to start tearing bits apart for inspection, or keep looking for other clues that will help diagnose.

    Seeing as you've ruled out air/fuel/spark, I still think it's most likely cooling related (though it would still be rare there's no limp mode or codes thrown by the temp/knock sensors), but maybe someone more knowledgeable will be able to read the issue better.

  6. #6
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    Quote Originally Posted by ryllz View Post
    What was the reason for the shortblock being replaced? If the setup was working great before and that was the only thing that's changed, then I guess your options are to either to start tearing bits apart for inspection, or keep looking for other clues that will help diagnose.

    Seeing as you've ruled out air/fuel/spark, I still think it's most likely cooling related (though it would still be rare there's no limp mode or codes thrown by the temp/knock sensors), but maybe someone more knowledgeable will be able to read the issue better.
    I ran it too lean. I believe it was a matter of me walking a fine line with the fuel regulator and air/fuel ratio, while at the same time not having enough fuel in the tank to maintain constant pressure.

  7. #7

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    I think it is fuel related. I wonder if it is running out of fuel. You could do a test with the fuel cap loose. If it is lean, then you need to be real careful.

    I know my ski acts rough whenever I take the rail off or disconnect the line. This is because the system gets air in it and you have to wait for the injectors to fire and clear out the air. Upon startup ski is rough and then clears out. This could be why it dies and does not set a code.

    If you have a Riva rail you could put a gauge on the end of the rail and long line and watch the fuel pressure.

    Map datalogger would show lean condition also. I would watch the battery volts on the dash at high rpm also.

    Robert

  8. #8
    I recommend change to a known to be good tuned ECU from a nearby buddy. It only takes a couple of minutes to try that.

  9. #9
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    Quote Originally Posted by OutlawGPR View Post
    I recommend change to a known to be good tuned ECU from a nearby buddy. It only takes a couple of minutes to try that.
    I thought about that, but unfortunately I don't have any buddies with an FX. If all fingers pointed to that, I would just buy a new ECU.

  10. #10
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    Quote Originally Posted by rcrisafulli View Post
    I think it is fuel related. I wonder if it is running out of fuel. You could do a test with the fuel cap loose. If it is lean, then you need to be real careful.

    I know my ski acts rough whenever I take the rail off or disconnect the line. This is because the system gets air in it and you have to wait for the injectors to fire and clear out the air. Upon startup ski is rough and then clears out. This could be why it dies and does not set a code.

    If you have a Riva rail you could put a gauge on the end of the rail and long line and watch the fuel pressure.

    Map datalogger would show lean condition also. I would watch the battery volts on the dash at high rpm also.

    Robert
    Robert, when the ski shuts down, I am in the low 11's. With that being the case, wouldn't that rule out a fuel issue?

    Also, I have run the ski for probably an hour and a half, so I'm not sure there would be air in the line anywhere.

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