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Fast Idle when HOT Stumped

SpeedwayRN

Tuned and Synch'ed
GT Contributor
Joined
Aug 4, 2011
Messages
46
Location
Justin, Tx USA
Still having problem with fast idle when the engine gets nice and hot up to operating temp.
Idles at 1800.
No error codes.
I have blocked off the stepper motor and all vacuum connections.
Checked all the boots and clamps and airbox for leaks.
Nothing seems abnormal. Even spraying WD40 around the throttle bodies and connections doesn't reveal any sort of air leak.
Removed and cleaned injectors.
TB stay balanced
Valves checked
I am stumped.
Any ideas?
 
Have you read the temperature sensors in real time? Something may be off getting the mix too rich or lean resulting in a fast idle. Also when you cleaned the injectors, did you clean the TB butterflies? Is more than one idle bypass screw open?
 
If you blocked off the stepper motor and it still idles high there is probably air getting in from somewhere. Adding more fuel (too rich) will not raise the idle, although too lean can cause a hanging idle but it usually will not stay up there.
Look for vacuum leaks. Has anybody messed with the "sacred screw"? Perhaps the throttle plates are just too far open at idle. Has it always done this? With the stepper blocked off there should not be enough air to idle that high.
 
If you blocked off the stepper motor and it still idles high there is probably air getting in from somewhere. Adding more fuel (too rich) will not raise the idle, although too lean can cause a hanging idle but it usually will not stay up there.
Look for vacuum leaks. Has anybody messed with the "sacred screw"? Perhaps the throttle plates are just too far open at idle. Has it always done this? With the stepper blocked off there should not be enough air to idle that high.
I got the bike with a few hundred miles. It seemed to develop after a few thousand miles. So the TB were set at factory specs. I have been chasing this for 12k miles or so. Only one bypass screw is now open. The throttle bodies are spotless. The yellow paint on the sacred screw appears to be in tact. When the motor is cold it idles at 1100 rpm. After riding it and getting it up to temp you come to a stop light and it won't idle lower than 1800. Even spraying with WD40 around all the rubber boots and throttle bodies no changes in RMP.
 
Kind of grasping at straws here, but have you checked the manifold connections at the head? There are some o-rings there that could be failing or the screws may have come loose.
 
Kind of grasping at straws here, but have you checked the manifold connections at the head? There are some o-rings there that could be failing or the screws may have come loose.
I have not but I have sprayed WD 40 all over the engine looking for leaks to no avail. I will check that though to be sure.
 
Be sure to check the lines from the output side of the stepper motor to the throttle bodies as well.
 
Be sure to check the lines from the output side of the stepper motor to the throttle bodies as well.
Thanks Todd
I have completely blocked all the stepper motor passages. The one that goes to the air box and the ones going to the throttle bodies. Sealed with thick vaccium caps and zip tied in place. The stepper motor is still bolted in place but neither the in or out is connected to the airbox or throttle bodies.
 
Did anyone ever find out what was causing the high idle? My 2008 Norge does the same thing and the dealer that I go to has no idea why.
 
Did you try any of the steps mentioned in this thread?
If so, what did you find?
No I just purchased the bike and took it to the dealer who tried to fix it. They set the throttle bodies and the TPS new injectors flashed the ECU. Still runs the same. I think I will look at the stepper motor next.
 
Still having problem with fast idle when the engine gets nice and hot up to operating temp.
Idles at 1800.
No error codes.
I have blocked off the stepper motor and all vacuum connections.
Checked all the boots and clamps and airbox for leaks.
Nothing seems abnormal. Even spraying WD40 around the throttle bodies and connections doesn't reveal any sort of air leak.
Removed and cleaned injectors.
TB stay balanced
Valves checked
I am stumped.
Any ideas?
I tried everything except cleaning and or replacing the O2 sensor. Even disconnected the stepper motor.
I just sold the bike to buy a Motus MST.
 
I tried everything except cleaning and or replacing the O2 sensor. Even disconnected the stepper motor.
I just sold the bike to buy a Motus MST.
Great looks like I am a lone on this one. The dealer doesn't know but they could start replacing parts until he gets it. Very expensive way to do things. The funny thing is it only idles at 1,800 RPM when you stop in gear with the clutch pulled in. If I put it in neutral and let the clutch out she goes right down to 1,100 RPM??????
 
Great looks like I am a lone on this one. The dealer doesn't know but they could start replacing parts until he gets it. Very expensive way to do things. The funny thing is it only idles at 1,800 RPM when you stop in gear with the clutch pulled in. If I put it in neutral and let the clutch out she goes right down to 1,100 RPM??????
Try cleaning the O2 sensor. That's next to free.
I have seen used O2 sensors for $35 on eBay.
Mine idles speed normal until it warmed up then idled at 1800-2000.
 
Actually, it may be a problem with the clutch switch. I ran into this on my '07 Norge. For some reason they tie the switch into the idle - I think it is done so as you release the clutch while in gear there is an automatic increase in RPM. But if the switch is bad (what happened with mine) the ECU seems to think it needs to up the idle to 1800. Something to check out anyway.
 
It has nothing to do with the clutch switch. The difference in RPM with the clutch in/out has to do the with friction from the clutch pushrod/flywheel. Your high idle issue has everything to do with the Stepper Motor. Well documented here... if you don't want to read above, do a search for Stepper Motor. You'll find plenty of info. I might just combine this thread.
 
Ok I read it again and if someone totally blocked the stepper motor don't you think it could be something else? What do you mean if I don't want to read what is above? This type of menu is for people to share with others the problems they have had and the fix to that problem. When I do find the problem and I will I will share the fix. You may be correct that it is the stepper motor time will tell.
 
Sorry, I didn't read clearly. If the Stepper motor is in fact completely blocked off, and if everything is to spec and the "sacred screw" that controls idle is still factory set, you'll still need to connect to the bike with some type of diagnostics tool to see if anything else is flagged. If al checks out there, then you may have an air leak.
Yes this Forum is to share problems, but the same subjects come up over the years, and it just takes a search and some reading to uncover 90% of the issues. There's more then 10 pages on this subject, is this section alone.

I'll be watching for what you find.
 
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