My 2008 sportster custom idle speed is quite normal (I feel). I do not have tach meter, cannot tell what rpm is. Every time, after 30 or more minutes highway ride, the idle speed jump high. The high rpm is high enough to roll the bike from 1st gear without adding any gas. However after around 30 seconds later, the idle speed changes back to normal (before highway ride). Is this normal for jet engine? I use 92 octane gas. Thanks for any input!

 

Mine doesn't do that.
If I shut it off and restart it, it will be at high idle for a minute or so even though its already hot but once it comes down to normal idle it stays down.

 

I have a similar problem but not always due to highway speeds (sometimes) and a lot of times when I'm revving high rpms on the twisties but can't seem to figure out exactly how to trigger it.

The difference with mine is that when I come to a complete stop it's at high idle but goes down to normal in about 5 seconds...yet it's still long enough to trigger diagnostic code P0505, which I believe is something to the effect of loss of idle control or something like that (google it)

I'm sure with 30 seconds your DTC has been triggered and your check engine light should be on.

I was thinking about getting this fixed but figured since it's only 5 seconds, I'll just let it be and just reset the code once in a while. However, for you 30 seconds seem like a bigger problem so I'd take it back to the stealership and see if they can fix it under warranty.

Good luck!

 

Hi jbyun,
first, thanks for your reply. While google my bike issue, I saw your thread at https://www.hdforums.com/forum/sport...ine-light.html

Here are the differences I compare both issues:
1) My check engine light never come up even during high idle. May be my engine light broken, or may be the rpm is not high enough to trigger it.
2) My bike issue only happens for long highway ride. If it is less than 20 minutes, I do not see same issue. My idle speed always behave normal during local ride regardless speed is 50, 40, 30..

Regardless engine light should be on or not for my high idle, I will have my local hd dealer check this issue soon. Unfortunate, bike warranty is expired, hope this issue will not cause my arms or legs.

Here is result from running diag
P: no rsp
S: none pn 68920-07
SP: none pn 67436-08
T: no rep
B: no rep

Do these numbers look normal?
Researching.....

 

Yeah without a tach, it's kind hard to describe how high the rpm is. But if I were to try, I'd say when it happens to me, the idle rpm is about the same as if you were to start up the bike cold in the winter. It's not screaming or anything but you can definitely tell it's working.

The engine light not triggering is kind of weird but the more I research my issue, there could be so many different things that can be causing it and since it doesn't seem to be a huge deal, I figured I'd just live with it.

It sounds like we have two different issues but best of luck to ya!

Btw, have you checked the DTC codes to see if you have any historical codes in your system? You might want to check.

 

jbyun, you are right. I do have ETC code P0505 stored.

Ran into this thread, and come out some areas which are possible causing P0505

Vacuum leaks - check for leaks

- Contaminated fuel

- Excessive Oil in crankcase

- TP sensor reading greater than 1 % (cable misadjusted), battery less then 9 Volts, or vehicle speed sensor (VSS) greater than 0 will disable idle speed control.

- Loss of battery power to terminal 31 of ECM.


https://www.hdforums.com/forum/sport...ode-p0505.html


Thanks for the reminder to check ETC code. This gives me a good start to research this issue.

 

That doesn't sound very good

I'm a n00b so don't know what most of those mean or where to start to diagnose the problem. Like I said, for me, it's almost a non-issue so I'm going to just let it be.

Hopefully, the dealer won't screw you too bad but just in case, don't forget to bring the KY.

 

Simple stuff first
engine off bike cold,,
Bars straight and at all turn angles,,
Are the throttle cables hanging up ??
They may need a cable lube job,,,
does It Snap back from WOT when you let go ??????

Air filter clean ?
Spark plugs clean ?

 

Osco, thanks for the tip. I checked it this morning, regardless full right or left turn, the idle speed is stable. I also rode it around 30 minutes on local road and highway, the high rpm issue does not show up.

Look like this issue only shows up after more 30 minutes highway ride, or probably should say after the engine running under high rpm consistently for period of time.

Not giving up yet, still researching issue......

 

If you ever figure it out, could you post updates on this thread or better yet, PM me? Might want to give your solution a try to see if that fixes it for me.

If you're gonna do the leg work, I'm just going to potentially reap the benefits