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150 HPDI Midrange Stumble

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  • 150 HPDI Midrange Stumble

    Hey guys, new season new issue. I could use some tuning help please. I have a 2003 Z150TXRB that I’m fighting with again. The engine idles perfect, can ***** for miles, and is now smooth at wot. However it bogs and stumbles at midrange. Coming out of the hole it will jump up and run if I go from idle to full throttle but will hesitate and bog if I ease into it. Also does this if I’m running wot and try to back down to around 3k-4K. It acts as if something isn’t synced quite right. I replaced the tps sensor and have checked the voltage and sync half dozen times with no improvement. TPS is .51 with linkage disconnected and .62 connected at idle, 4.19 wot. No current codes on YDS and tps voltage advances smooth with throttle. Throttle valve angle is 2.2 at idle and 77 at wot. Does it sound like something is out of sync or possibly the timing curve off? Timing is showing 4 BTDC idle and 18 BTDC wot. Fuel pressure is 49 psi at vst consistent and 729 psi idle, 795 psi wot at the high pressure pump. I’m a little over propped, 5100 rpm wot. I’ve ordered a smaller pitch to correct this but seems like something is off in the tune. What do you guys think I should check? All help is greatly appreciated.

  • #2
    what was the rail pressure while the problem shows up?
    what about timing?
    need to look to see if something is changing when problem shows up


    • #3
      I’m going to try to make another run tomorrow if the rain stops here. I’ll try to set something up to record the yds screen while I run it.