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  1. #1

    2006 Seadoo Sportster backfire problem

    I have a 2006 Seadoo Sportster 4tec 215 SCIC with about 120 hours. When I bought it a year ago, it ran perfect. After a couple of tankfulls, it started having this problem..
    At 2000-4000 RPM, it will backfire, I believe it's an exhaust backfire. It does this more after it has warmed up. Starts fine, idles fine, accelerates fine and runs at full throttle no problems. If i accelerate slowly from idle after warm up, it will backfire once or twice until I get up over 5000RPM, then no problems. If I accelerate quickly from idle, no problem. After cruising endlessly above 5000 RPM or more, if I try to go below that, say 25-35 MPH, it will backfire, not continuously, just once or twice, until I bring it back up over 5000 RPM.
    I'm completely perplexed by this. I took it to the dealer, they said it was the computer, I replaced that and still does the same thing. I've swapped out the coils from my ski (same engine), problem still persists. I've changed the plugs of course, checked for bad hoses, vacuum leaks, etc... nothing. I've redesigned the air intake to receive fresh air from the outside, none from the engine compartment.. still backfires. I've also changed the TPS even though it didn't show bad. I have the BUDS system, it shows no codes, nothing out of the ordinary, same thing with CanDoo Pro. Like I said, I can run at full throttle all day long, no problems, runs perfect. Always starts and idles perfect, hot or cold. Have tried winter and summer gas blends, no difference.
    I just wanted to know if anyone has an idea where I could check that I might have overlooked. I am a pretty good mechanic (not by trade) and I've racked my brain trying to figure this out. Why would I get this backfire only at that RPM range? Any ideas would be greatly appreciated!


  2. #2
    Fuel filters? My 05 would studder occasionally in that rpm range to the point it would shake the boat and replacing the filters in the fuel pump resolved it. Ran fine at all other rpms too.

  3. #3
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    leaky injector...and for pete's sakes change the plugs if you haven't

    how's the oil, if it smells like fuel, without fail a leaky injector

    at high rpm, you can even get away with a leaky valve.

    backfiring will eventually split a plastic resonator and that will sink you

    I hope you held onto the old ecu. I doubt that's the root of this issue

  4. #4
    Quote Originally Posted by brent View Post
    Fuel filters? My 05 would studder occasionally in that rpm range to the point it would shake the boat and replacing the filters in the fuel pump resolved it. Ran fine at all other rpms too.
    I thought about the fuel filter but I figured a dirty one would be more evident at full throttle, not at quarter throttle but.. good suggestion, I agree that I should replace the filter, thx.

  5. #5
    Quote Originally Posted by Seedew View Post
    I thought about the fuel filter but I figured a dirty one would be more evident at full throttle, not at quarter throttle but.. good suggestion, I agree that I should replace the filter, thx.
    Airtex Part numbers for the filters
    Outer Fuel Filter:FS242
    Inner: FS220

  6. #6
    Quote Originally Posted by nmpeter View Post
    leaky injector...and for pete's sakes change the plugs if you haven't

    how's the oil, if it smells like fuel, without fail a leaky injector

    at high rpm, you can even get away with a leaky valve.

    backfiring will eventually split a plastic resonator and that will sink you

    I hope you held onto the old ecu. I doubt that's the root of this issue
    Actually, that was going to be my next try at this. My jetski, which has no problems, has the same injectors, I was going to just swap the fuel rail with injectors attached. As far as plugs, I know these engines eat plugs for breakfast so I buy them a box 0f 20 at a time. I change them very often. I also change the oil regularly, this boat has fresh OEM oil/filter. I do have the old ECU (they aren't cheap) and I agree this backfiring isn't doing the engine any good which is why I'm desperately trying to come up with a resolve. In the mean time, I can drive it pretty much all day without having it backfire if I'm careful with the speed/throttle.
    Thanks for the input, much appreciated.

  7. #7
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    2006 Seadoo Sportster backfire problem

    If you donít have an otiker clamp to reattach the fuel rail at the least used double worm gear clamps until youíre ready to button it up, then put the correct clamp in place

    Relieve fuel pressure before removing lines

  8. #8
    Quote Originally Posted by nmpeter View Post
    If you don’t have an otiker clamp to reattach the fuel rail at the least used double worm gear clamps until you’re ready to button it up, then put the correct clamp in place

    Relieve fuel pressure before removing lines
    I do have an assortment of Otiker clamps so I'll definitely make sure I use those after I'm done swapping out the rail. I learned many years ago to relieve the pressure first.. got it right in the face!
    Thanks for the tip.

  9. #9
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    And?......

  10. #10
    I haven't swapped the injectors yet. I'm not totally convinced that would be the culprit. If an injector were faulty in some way, why is it that it starts and idles perfectly and accelerates under moderate to full throttle perfectly and runs at 35MPH and above with no problems. Why would it backfire only at light throttle.. idle to 30 MPH? If an injector was slightly plugged or electronically not injecting correctly, wouldn't that be felt throughout the entire RPM range? I'm not sure if an injector can misfire, very consistently by the way, only at certain RPMs/load. I thought fuel pressure was constant and the injector pulses, less at low RPM, more at higher RPMs. Am I missing something here?

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