Motor sneezing??
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Cruiser
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Motor sneezing??
Well some of you may have read a thread I posted in November about the MoCo giving me a new motor after it blew up on my 2006 Street Glide. Well I have noticed on occasion the motor hesitates after I have let off the gas and gas it asain. When I hit the gas again it sneezes then hesitates and then pulls normally. It only does it if I hit the gas quickly. If I roll into it slowly it never does it. I have a big sucker air intake kit and a set of mildly loud Wild Pig slip ons. It does not have a map that I am aware of. I never had this issue with the original motor. Any ideas??
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From: Phoenix '53, '88, '09 Big Twins
when you rapidly open the throttle you get more air ( remember throttle controls air into the motor) than the usual 14:1 ratio ( more or less) of air/fuel causing a sudden momentary lean condition.
lean condition can cause a sneeze through the intake.
your ECM isn't adding a blast of extra fuel to complement the air you are adding- so you need to find a tuning type solution.
( this is why carbs have an accelerator pump which squirts raw fuel into the throat when the throttle is quickly opened)
other causes are timing too advanced, combustion chamber temps too high ( which has the effect of timing being advanced) or a cam timing/ pushrod adjustment problem which has the valves out of proper timing - or bent valve/ bad seat etc.
these causes are listed in order of probability
mike
lean condition can cause a sneeze through the intake.
your ECM isn't adding a blast of extra fuel to complement the air you are adding- so you need to find a tuning type solution.
( this is why carbs have an accelerator pump which squirts raw fuel into the throat when the throttle is quickly opened)
other causes are timing too advanced, combustion chamber temps too high ( which has the effect of timing being advanced) or a cam timing/ pushrod adjustment problem which has the valves out of proper timing - or bent valve/ bad seat etc.
these causes are listed in order of probability
mike
Last edited by mkguitar; Apr 28, 2012 at 02:35 AM.
Tourer
Joined: May 2010
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If you are running a high flow a/c and mufflers, you better get some kind of tuner on that motor, or it won't last very long. The motors are relatively lean from the factory to pass EPA regs, the mods you have move air more efficiently and need more fuel thrown at it, otherwise the motor runs too lean, and performs like you are mentioning. I would go out on a limb here and bet that if you remove your heat shields, your pipes are going to be a dark shade of purple, and will be like that for quite a ways down the pipe.
I would avoid the dealer download as the entire motor company is subject to EPA regs. It would be better then what you have, but still not perfect performance wise. I went with a PCIII from fuel moto, and am very happy I did. I put the PCIII, big sucker and screamin eagle slips on all at once, and man what a difference.
Since then I went to a 2/1 propipe, sent an e-mail to Keith, and had a map the next day that worked out perfectly. I changed cams shortly after that, and again, he had a map that worked, and had it to me the next day.
No matter which way you choose, you need to richen up your mixture or YOU WILL BURN UP THAT NEW MOTOR PRE-MATURELY.
I would avoid the dealer download as the entire motor company is subject to EPA regs. It would be better then what you have, but still not perfect performance wise. I went with a PCIII from fuel moto, and am very happy I did. I put the PCIII, big sucker and screamin eagle slips on all at once, and man what a difference.
Since then I went to a 2/1 propipe, sent an e-mail to Keith, and had a map the next day that worked out perfectly. I changed cams shortly after that, and again, he had a map that worked, and had it to me the next day.
No matter which way you choose, you need to richen up your mixture or YOU WILL BURN UP THAT NEW MOTOR PRE-MATURELY.
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Joined: Nov 2006
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From: Mass
when you rapidly open the throttle you get more air ( remember throttle controls air into the motor) than the usual 14:1 ratio ( more or less) of air/fuel causing a sudden momentary lean condition.
lean condition can cause a sneeze through the intake.
your ECM isn't adding a blast of extra fuel to complement the air you are adding- so you need to find a tuning type solution.
( this is why carbs have an accelerator pump which squirts raw fuel into the throat when the throttle is quickly opened)
other causes are timing too advanced, combustion chamber temps too high ( which has the effect of timing being advanced) or a cam timing/ pushrod adjustment problem which has the valves out of proper timing - or bent valve/ bad seat etc.
these causes are listed in order of probability
mike
lean condition can cause a sneeze through the intake.
your ECM isn't adding a blast of extra fuel to complement the air you are adding- so you need to find a tuning type solution.
( this is why carbs have an accelerator pump which squirts raw fuel into the throat when the throttle is quickly opened)
other causes are timing too advanced, combustion chamber temps too high ( which has the effect of timing being advanced) or a cam timing/ pushrod adjustment problem which has the valves out of proper timing - or bent valve/ bad seat etc.
these causes are listed in order of probability
mike
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Cruiser
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From:
Ok it looks like motor is to lean according to all the great information I have gathered here. My next question so what is better the PC III or the SERT? Also which one is easier to use I.E. program myself with a laptop or whatever is used??
Thanks,
Mike
Thanks,
Mike
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From: Phoenix '53, '88, '09 Big Twins
I'm staying out of the tuner thing- I waited until the 09 MY to get a twin cam as I didn't want to be saddled with the EFI of the first 2 generations ( magnetti-marelli and delfi w/o lambda).
so the sneeze happens when vacuum is low ( whacked open throttle).
does it happen if the throttle is opened more gradually ?
can you determine at which rpm (s) this happens ?
if you can make note of rpms and throttle position or throttle position change, this info will be useful to anyone tuning your bike, which ever method they use.
mike
so the sneeze happens when vacuum is low ( whacked open throttle).
does it happen if the throttle is opened more gradually ?
can you determine at which rpm (s) this happens ?
if you can make note of rpms and throttle position or throttle position change, this info will be useful to anyone tuning your bike, which ever method they use.
mike
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Cruiser
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From:
I'm staying out of the tuner thing- I waited until the 09 MY to get a twin cam as I didn't want to be saddled with the EFI of the first 2 generations ( magnetti-marelli and delfi w/o lambda).
so the sneeze happens when vacuum is low ( whacked open throttle).
does it happen if the throttle is opened more gradually ?
can you determine at which rpm (s) this happens ?
if you can make note of rpms and throttle position or throttle position change, this info will be useful to anyone tuning your bike, which ever method they use.
mike
so the sneeze happens when vacuum is low ( whacked open throttle).
does it happen if the throttle is opened more gradually ?
can you determine at which rpm (s) this happens ?
if you can make note of rpms and throttle position or throttle position change, this info will be useful to anyone tuning your bike, which ever method they use.
mike
Never happens when the throttle is opened gradually.
Thanks
