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Discussion Starter · #1 ·
40hrs - 2017 Kawasaki Ultra LX 1500 non supercharged

Engine runs fine at light throttles and full throttle. At a certain part throttle range, it has instant power loss then back again, which can be several times a second until I gas on or reduce throttle. At times, more so after the first occurrence, when it returns to idle it’s sitting at 2000 rpm rather than 1300, and after a few more attempts it can return to a rolling idle, hunting up and down. A key cycle usually fixes any of the idle issues, but if I shut it down and restart, it can do a start-run-stall until I pull the key completely.

Findings and changes:

  • Replaced spark plugs
  • Found some water in tank initially, then removed - replaced fuel with new fuel
  • Purged fuel lines, but injectors haven’t yet been removed.
  • Replaced fuel pump and pickup sock, but not reg or the round filter? attached to the reg.
  • Fitted fuel pressure gauge to end of fuel rail. Although the needle bounces around a lot, there doesn’t seem to be any major changes when the issue occurs. Video recording of the gauge in the link below.

I pulled one of the injector plugs off and measured the voltage during the issue and nothing seemed to change.

No errors or codes on dash.

Thinking that it may be spark related, given the speed that the power stops and starts, and when running with the seat off I could hear the odd pop (minor backfire).

Looking for any advice / suggestions please, as I’m running out of ideas.

Part throttle launch, surging then applying more throttle to push through issue

Same as about, but with fuel pressure gauge attached to engine.
 

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I had a similar problem with a Toyota minivan and it turned out to be plug wires. I put one of those inline spark testers between the wire and the plug and I could see the skipping arc. Plug wires solved a problem that I had been chasing for a month.

40hrs - 2017 Kawasaki Ultra LX 1500 non supercharged

Engine runs fine at light throttles and full throttle. At a certain part throttle range, it has instant power loss then back again, which can be several times a second until I gas on or reduce throttle. At times, more so after the first occurrence, when it returns to idle it’s sitting at 2000 rpm rather than 1300, and after a few more attempts it can return to a rolling idle, hunting up and down. A key cycle usually fixes any of the idle issues, but if I shut it down and restart, it can do a start-run-stall until I pull the key completely.

Findings and changes:

  • Replaced spark plugs
  • Found some water in tank initially, then removed - replaced fuel with new fuel
  • Purged fuel lines, but injectors haven’t yet been removed.
  • Replaced fuel pump and pickup sock, but not reg or the round filter? attached to the reg.
  • Fitted fuel pressure gauge to end of fuel rail. Although the needle bounces around a lot, there doesn’t seem to be any major changes when the issue occurs. Video recording of the gauge in the link below.

I pulled one of the injector plugs off and measured the voltage during the issue and nothing seemed to change.

No errors or codes on dash.

Thinking that it may be spark related, given the speed that the power stops and starts, and when running with the seat off I could hear the odd pop (minor backfire).

Looking for any advice / suggestions please, as I’m running out of ideas.

Part throttle launch, surging then applying more throttle to push through issue

Same as about, but with fuel pressure gauge attached to engine.
 

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2 Posts
Discussion Starter · #3 ·
I had a similar problem with a Toyota minivan and it turned out to be plug wires. I put one of those inline spark testers between the wire and the plug and I could see the skipping arc. Plug wires solved a problem that I had been chasing for a month.
Thanks for the suggestion Beef. I’m thinking it would have to be all 4 leads that had the issue as it isn’t a single cylinder misfire, it’s all cylinders.
I’m wondering if it’s an intermittent sensor fault (like the rollover sensor), which limits the engine speed to 3000 rpm via cutting the spark?
 
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