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[Jetmech30]

Has anybody had the m8 upon slowing down to stop have there idle surge up and down?

[IA17RGU]

Mine just started that. 25,000 miles. I only noticed all of it happening it in the rain


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[Jetmech30]

Never been in the rain.. only seems to do it after long rides!! Maybe a sensor?

[1roadking]

Sumoing?

[grc]

Never been in the rain.. only seems to do it after long rides!! Maybe a sensor?

Could be a sensor (TPS/TMAP/etc), could also be a small vacuum leak.  Very possibly heat related, since it only occurs after a long ride.  If you know a good conscientious Harley tech, have him do the full diagnostics.  If your dealership is like many, be prepared to be blown off if you just ride in, tell them the symptoms, and ask them to fix it.  Still report it, just be aware that in many shops anything that requires a little head scratching and diagnostics tends to be blown off as normal, they all do that, couldn't recreate the problem, etc.

JMHO - Jerry

[hrdtail78]

A lean idle can cause it.  The more heat that is in the engine.  The less fuel is going to be delivered.  (to a point)   Do you have a tuner on the bike.  For test you could take that area out of closed loop by targeting a richer AFR.  If it is cause by leaness.  It should go away.  If so, then you could target a richer AFR that is still with in closed loop if possible.

[Jetmech30]

Thank you all for in put on this issue... I do have PV I’m going to hook it up and try and do an auto tune see what’s happens!! .. it only seems to do it when temps are high... when I come to a complete stop it stops ??