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  1. #1

    MSX150 Overboost protection mode

    This spring I finally removed the intercooler to fix the contamination issue. Previous to this my MSX150 would typically run to about 6,500 rpm and regularly run up to 7,500 rpm but not all the time. I had a lot of irratic idle problems. I removed and cleaned the intercooler and replace MAP sensors. My idle is now corrected (it sometimes takes 10 seconds for it to settle in to 1500 - 1600) but the ski is mostly in overboost protection mode i.e. 4700 rpm with occasional runs to 5,700 rpm. Wastegate is free and I can't seem to find anything obviously wrong. Any suggestions?


  2. #2
    ripcuda's Avatar
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    Howdy,

    Are you getting any check engine indicators or flashing red warning light on the display? How about when it rev-limits?

    Have you run a compression test on your engine lately?

    Could be a failing/fritzing wastegate solenoid... that's working sometimes. If this fails... it almost always fails in the unpowered ("off") position where no boost goes to the wastegate actuator... and you overboost.

    Is your wastegate solenoid the old version... attached to the front side of the turbo... or the updated version... on the bracket off the valve cover over top the exhaust manifold? Old versions are likely to fail... thus the updated version.

    Also... double check all intake hoses for tight clamps and no tears or punctures. A popped hose will only get around 5800rpm w/o boost to drive it the rest of the way to redline.

    Cheers!

  3. #3
    Thanks. No check engine lights. I believe the wastegate solenoid is the correct update version, grey with two attached hoses and one open nipple. It's mounted to a bracket on the valve cover. Since I had intermittent full boost before removing intercooler, seems the most likely cause may be intake hose since I had them off. I have run it to 5800 on occasion but now it seems to go to overboost protection...that's what is puzzling me.

  4. #4
    By the way. I always check compression with throttle open, how is that accomplished with ETC?

  5. #5
    ripcuda's Avatar
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    If your triggering overboost... and getting the limp mode... that wouldn't be from a popped hose. If you had a boost leak, the pressure inside the hardpipe/intake could never get high enough for the MAP sensors to read too much boost. A boost leak will just give you no top end. I'll run sorta normal up to about half throttle... then as the boost starts to come on... it leaks and power plateaus. It'll only get to around 5900 max rpms (my experience).

    Overboost is going to be a seized or sticking wastegate on the turbo (common), a bad wastegate solenoid (common), a bad wastegate actuator (rare), a missing/popped-off hose boost source hose to the solenoid or from solenoid to actuator.

    When doing a compression test on the Weber... squeeze full throttle as you crank. This will full-open the ETB and it'll shut off fuel injectors (at least it's supposed to) to aid starting if the engine was flooded.

    Cheers!

  6. #6
    Thanks Ripcuda. I found an intake hose was leaking. This improved performance 100% and when running yesterday I was able to run up to 7,700 rpm. However, after running a few times, the last time out I was limited to 6,300 rpm. I also experienced some erratic idle, 1,700 to 2,000 surging. Sounds like contaminated MAPs again?

  7. #7
    ripcuda's Avatar
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    Yeah... did you remove the intercooler to clean it out? If not... there is probably some oily gunk settled down there that's rearing it's ugly head under max boost. This is probably fouling your hardpipe MAP... the one that uses the air temp sensor (the part that gets fouled). Pull both MAPs... and swap them. If the intake MAP didn't get oil fouled... it's air temp sensor will still be okay... while the other one will be fine as a pressure sensor only on the side of the intake manifold. Worth a try.

    But yeah... pull the hardpipe... see if you got more gunk in there. Clean and repeat.

    Cheers!

  8. #8
    Thanks, I will give it a shot. I did remove the intercooler and cleaned the stink out of it with degreaser, then soapy water then steam. I did not scrub all the intake hardware. I'll give it a shot. Again, thanks for the advice.

  9. #9
    ripcuda's Avatar
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    I'd also recommend... if I haven't already... to ditch the oil vapor recirc emissions hose that comes off the oil separator (cyclone thing on battery side of oil tank) and goes to the airbox (turbo inlet). This hose is the main reason for oil ingestion. Remove the hose and get a shorter piece to plumb from the oil separator into an oil catch can. Say goodbye to future oil ingestion.

    Cheers!
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