dave_424
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| posted on 14/11/16 at 01:28 PM |
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Hayabusa missfire
Hi guys, currently working on a gen 1 busa that seems to be issuing at low rpm/idle. When you open the throttle, the engine holds at around 2k rpm,
like a 2-step rev limiter. If you snap the throttle open, it can backfire up through the throttle bodies
If you can get it up to around 4k rpm, it all clears and runs fine until you drop back down in rpm.
Checked coils and just had new plugs.
If the map sensor is unplugged from its vacuum source, but still connected electrically, the engine runs absolutely perfect, at all rpm.
Map sensor gives 3.66v at atmospheric, dropping to 1.7v when sucking on its vacuum pipe
Am I missing something or is it just a dodgy map sensor? They aren't cheap so wanted to hear your opinions
Thanks
Dave
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Jon Ison
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| posted on 14/11/16 at 04:43 PM |
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The only misfires I have ever had have been plugs which you have changed and a battery breaking down, had me scratching my head 1/2 way through a
track day as it showed plenty of voltage but under load had nothing behind it.
Same symptoms as you describe once the engine was spinning fast enough and making enough power to compensate the misfire went away, worth checking?
eta, if you do need a MAP sensor ring Malc at Yorkshire engines, he's as straight as they come and very fair on prices.
[Edited on 14/11/16 by Jon Ison]
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Andy B
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| posted on 14/11/16 at 05:26 PM |
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Sounds like map sensor all day long - will give exactly that symptom when it goes down - had one last year doing the same thing - might be worth
borrowing one to double check first but that's where my money would be
regards
Andy
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