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  1. #1

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    MSX 150 RPM Throttle issue

    Ran fine for the first couple of times out this year, but then started going into limp home mode, right after hitting about 5500-6000rpm. Actually I thought it was a boost issue because that is about when it started to go into boost. This weekend I tested most of the sensors and didn't find anything wrong other than maybe the exhaust temp sensor. Taped the wire, but no go. Then I thought lets do a relearn on the PPU/ETB. I have the inner cooler pipe off and when I started to move the throttle, the etb jumped but didn't really move. I messed with it a bit and found some corrosion on the PPU connector wires, so I will clean that. Then I found that I could only open the blade in the throttle body about 1/3rd of the way open, so I took the ETB off. I had to pry the blade open with a screw driver, but then it wouldn't close. I cleaned it and sprayed some penetrating oil on it and it is somewhat losened up, but it still sticks a little. Anyways I pulled the plate off the side and don't see any real issue in there. I did bend a few of those scrubbing wires but bent them back into place so hopefully it's ok, but I am thinking this thing needs replaced. I don't really want to keep having issues with the throttle body opening smoothly and causing the computer to make it shutdown. The throttle plate should have opened at least to that point of stopping, so is my PPU maybe a problem also other than the corroded connector? Thing was running great after getting the ECU upgrade from PrecisionSports last year.


  2. #2
    ripcuda's Avatar
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    As you do the ETB Relearn... you should see the butterfly open fully and close fully in sync with your throttle trigger input. If it's sticking part way or not closing... that is clearly an ETB problem.

    The ECU has dual throttle position sensors in the ETB. If they are off... it goes into limp home mode as I suspect you are seeing. If you could pull codes... I'd bet you see the one for the ETB throttle position sensors.

    The PPU (pedal position unit) is the back unit under the front steering where the actual throttle trigger cable connects to. Sounds like that is working fine. Your actual ETB sounds very suspect based on your description.

    Put the lanyard in, tap the start button (don't start)... and you should be able to open/close the throttle (synced with the ETB butterfly) all day long smoothly without any issues. If it doesn't... it's not working right.

    If you needed a new one... I'd look for a very clean, low hour used one here or on fleabay (MSX 110 or 150... same same).

    Cheers!

  3. #3

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    Thanks ripcuda, I found a used ETB on fleabay for $60, so we'll see what happens after I get that in and clean the PPU connections. In the past learning processes it has always opened and closed via your process. It's just strange that the it is catching and hanging up. The butterfly is clearly not catching anything so it is in the shaft somewhere. There isn't much to it, just another butterfly on a throttle body which should last a lifetime. There wasn't any corrosion and it wasn't really dirty or gummed up. I guess we'll see.

  4. #4
    ripcuda's Avatar
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    Yeah... I've heard of an ETB or two going bad... but it's not really common. When they do it usually the internal butterfly motor... which sounds like your case. Hope that newer ETB gets you going!

    Cheers!

  5. #5
    Quote Originally Posted by rockien View Post
    Ran fine for the first couple of times out this year, but then started going into limp home mode, right after hitting about 5500-6000rpm. Actually I thought it was a boost issue because that is about when it started to go into boost. This weekend I tested most of the sensors and didn't find anything wrong other than maybe the exhaust temp sensor. Taped the wire, but no go. Then I thought lets do a relearn on the PPU/ETB. I have the inner cooler pipe off and when I started to move the throttle, the etb jumped but didn't really move. I messed with it a bit and found some corrosion on the PPU connector wires, so I will clean that. Then I found that I could only open the blade in the throttle body about 1/3rd of the way open, so I took the ETB off. I had to pry the blade open with a screw driver, but then it wouldn't close. I cleaned it and sprayed some penetrating oil on it and it is somewhat losened up, but it still sticks a little. Anyways I pulled the plate off the side and don't see any real issue in there. I did bend a few of those scrubbing wires but bent them back into place so hopefully it's ok, but I am thinking this thing needs replaced. I don't really want to keep having issues with the throttle body opening smoothly and causing the computer to make it shutdown. The throttle plate should have opened at least to that point of stopping, so is my PPU maybe a problem also other than the corroded connector? Thing was running great after getting the ECU upgrade from PrecisionSports last year.

    I have a similar issue with my msx 150 after an afternoon of running perfectly it went into limp mode then in and out of limp mode limited to about 3300 rpm and I tried to do an ETB relearn and I am getting very little movement of the butterfly but I can push the butterfly wide open with my hand but not with throttle have you sorted out your problem yet ?

  6. #6
    Mike Greenwood's Avatar
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    What was the button trick to reset the throttle?

  7. #7
    ripcuda's Avatar
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    ETB Relearn procedure:
    Engine off
    - insert lanyard
    - tap start button... but do NOT start engine... just wake system up... should hear the fuel pump hum and ETB click
    - slowly squeeze throttle trigger to full... pause 2 secs
    - slowly release trigger to zero... pause 2 secs
    - repeat twice more
    - pull lanyard out
    - wait a few minutes

    This will remap the ETB throttle sweep in the ECU.
    This needs done when you replace the ECU or ETB.

    Cheers!

  8. #8

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    Well I installed the used ETB yesterday and I thought I did the relearn, but I may have not completed it correctly. So I will go do it again with your method. I've seen about different methods. All are similar, but not the same. It idles fine but when you give it throttle it goes to 4800 and no more. I know that usually indicates over boost. I swapped back to my original ETB and it has the same problem. Last week I tested all of the sensors I could get to along with the waste gate solenoid and disconnected the arm. The waste gate is free and not binding.. If the PPU & ETB is out of sync will it cause this type of rev limit? I post again after doing the relearn and testing again.

  9. #9
    ripcuda's Avatar
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    Are you getting a CEL?

    The PPU and ETB both have dual position sensors in them. If they fail or read differently, the ECU goes into limp-home mode (1750 rpm limit)... and throws a code... so should be pretty easy to spot.

    When you preform the ETB relean... have the IC-to-intake hardpipe off... so you can watch the ETB sweep the throttle plate. Ensure it goes full open and full close... smoothly... in sync with the throttle trigger you are moving.

    A solid 4800 rpm limit by the ECU is for overboost. This is pretty easy to see. The engine/ski surges as boost comes on hard... then hits a wall and the party is stopped. Is this happening to you? Or is it just petering out at ~4800?

    How did you disconnect the WGA rod/arm? If you adjusted the turn-buckle nut... with locking nuts on either side... then you will need to get this set back to proper length... or the ECU will struggle to control boost.

    Cheers!

  10. #10

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    Thanks for the input ripcuda. Now I feel stupid, after checking all of the sensors and stuff last week, I didn't get the wires connected back up to the boost solenoid. I reconnected it, did the relearn with your procedure and watched the ETB. Took a test drive and BAM, it run great once again. So my problem was definitely the ETB. I think I could use my old one, but it still has a rough spot and catches. The new (used) one is as smooth as butter. We'll see how it does the rest of the day on the water.

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