I haven't researched this in the service manual yet, but thought maybe someone here has experienced this annoying problem.
2008 Ultra w/throttle by wire. Idling about 1800rpm. Roll the throttle forward slightly and I get normal idle. Take hand off of throttle and it returns to 1800rpm.
This doesnt seem to be the same issue as the fast idle where I can cycle the switch 3 times to reset the computer and eliminate the problem. I've encountered that several times in the past.
This is different and seems to be in the throttle/potentiometer. Anyone know if theres an adjustment, or lubrication point on the throttle mechanism? Or is it just replace the potentiometer? First problem I've experienced with this system.

 

Have you replaced the hand grips, or made any adjustments to the grip? The reason I ask this is because, if you have no play in the grip, as in, if you try and move it in and out on the bar and it does not move a little, then it is too tight and will stick. Loosen the clamp and slide the assembly out a fraction and tighten back.

If the above was not the problem and you already reset the idle by the method you mentioned, then I would say maybe your TGS is going bad, but I may be wrong.

 

See if you can measure the signal voltage from the TPS. If it's high at idle without you touching it and then it drops when you move it forward to "normal idle" (I think around 0.8V) then you're either adjusted too much, or the sensor itself may be bad. I've seen a lot of sensors with dead spots in them but I don't think I've ever seen this..

 

Seems I read somewhere on here about a process to "reset" the home position of the throttle sensor. From what I took from the thread it allows the current resting throttle position to correlate with normal idle rpm.

 

Whenever I had to reset the throttle (cycle 3 times), I always had this symptom. So, in my experience it was the same amimal. Idle high and if I rolled the throttle forward it would idle normal. After resetting all was good. I know you said that this seems like a different issue, but have you tried resetting yet?

 

I am going to go with resetting the idle speed like the two above me.

 

I had same issue months ago, but fixed it recalibrating the sensor (switching on/off some times allowing it to "sleep" between off and on for 30 secs).

Since then no more issues, but always switch on the bike with my right hand (not to inadvertently move the grip at power on).

Hope this helps, regards.

 

The '08s have a quirk,if you switch the bike off with the throttle rotated it will reset the idle speed. Usually this happens when stretching your thumb to hit the kill switch.
To reset it:
Turn the ignition switch on and off 4 times, pause for a few seconds in each position and don't touch the throttle.

 

This happened to me exactly Also had a small piece of rubber from the grip get in the gears and the throttle wouldn't return to idle

 

piasspj....You saved my *** with this reply....Thank You