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idle all over the place

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AliveAgain

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The bike is a 2006 FLHTCUI with 20,000 miles on it. After some stop and go riding the bike will idle down to 500 rpms. After riding on the highway for half an hour, the bike won't go below 2000 rpms even at a stop. I've checked for leaks, cleaned out the iac port, made sure the cables were lubed and checked that the inlet plate fully closes. The issues seem to become more prominent when the temp starts to rise outside. In 40* weather no problems but when it gets to 60* the issues come up. I don't want to just start replacing parts so any help would be appreciated. thanx.
 
You may also want to check to see if you have any historical/current codes. If you do, read and record them. Clear the error log and give the bike a ride. Keep an eye on the check engine light and as soon as you get a hit, read the codes once again. Start with that code.
 
As I have said in the first post, I have cleaned out the Iac ( multiple times as a matter of fact) with no change. I checked for codes and there were none. The check engine light has never come on while running. In checking for tps, do you mean checking the voltage? Is it like other bikes that can develop a weak spot in the tp where the bike runs steady and give a false reading?
 
It would be nice to have a scan tool to check out the problem but you could check the tps with a DVOM. Sound like may be the IAC is going out and searching for the correct idle point. That is a problem with IAC losing the counts and the computer not picking up a code. One thing you could try is to see if the bike is able to set a IAC code with it unplugged. Good luck and hope you find the trouble soon.
 
AliveAgain said:
I checked for codes and there were none. The check engine light has never come on while running.
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You have performed a WOW test and there were no codes. You also have never seen the Check Engine Light come on during a riding cycle. I will assume that other than an idle speed issue,, the bike has no other engine performance problems such as flat spots in the throttle response.

Then my shot in dark guess would be the IAC is still sticking. Remember that the IAC has no feedback to the ECM. The ECM sends out a step correction amount. If the IAC performs it, then all is fine. But there is a limit to the step count. Does the diagnostic firmware say to itself "I have sent 100 steps to the IAC and the idle is still too high, it's time to throw a code". I don't think so. If you had a SEST kit you could see what step position the ECM thinks the IAC is at and you would know what was going on..

My guess is the stepper motor is still mechanically binding. There is nothing wrong with either phasing coil of the stepper or else the ECM would have thrown a IAC code by now. That is all the diagnostics can tell you. I think it only knows if Phase A or Phase B coils are open circuit. If you had a flat spot in the TPS, it would have to be near the butterfly closed position for the throttle body. Then I think you would also have drivability issues with the bike. (lack of electronic acceleration pump,,an off idle bog, etc and you don't)
 
My opinion like Hoople is that the IAC isn sticking at times. Probably could be solved with a good cleaning of the MOTOR and slide section. If not a replacement would be in order.
 
This is a shot in the dark, 07 models had a torque smoothing download that took care of this problem on my Streetbob, may be it is the same problem you are facing, call the dealer with your VIN
 
Thanks for all the replies. When I cleaned out the IAC, I did this by sticking the straw up the hole and blasting it for awhile. I stopped when it kept coming out clear. I will look at removing the assembly. I thought you had to remove the entire inlet assembly to do this. I have no flat spots while riding and had a good map made for it. I questioned about the tps because I have a Kawasaki which might give you a good signal reading at WFO and WFC and still have a bad TPS signal in the middle. While having a map made, the tuner reset the idle to 0% instead of the 5% it was reading. Will this effect the bike?
 
Anther shot in the dark here , If I remember there was a injector angle change early on in 06 production they went from a 08 to a 25, I dont remember if this was a recall or what the symptons were for the early 06 production run, but somthing to check in to,the injectors will have the number on them , check to see if there was a recall , I believe this injector change had somthing to do with a new valves stem sizes they did in 06.
 
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