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High Idle Only at Stop

5K views 25 replies 14 participants last post by  Heftysmurf 
#1 ·
I have an interesting problem along with the rare occurrence of not seeing it already answered via a search. My engine is idling high only after warm and coming to a stop. Honestly it is when I am going lower than about 2 mph and only once it is all the way up to operating temperature. It idles right at 1000 when at the top of my neighborhood. It stays ~ 1000 when rolling then raises just before I get to a stop.

Issues started a few weeks ago when it sounded like I had a vacuum leak (wavering idle) so I replaced all of the intake rubber...then removed the LCV and the vacuum problem went away but the high idle remains.

- Cold after startup: Idles at ~ 700
- Warm rolling: Idles at ~ 1000
- Warm stopped: Idles at ~ 1300

Engine mods: all of them. 110, heads, cam, PCV (on auto-tune since before the issue), coils, BAK, custom pipe, etc.

Any ideas?
 
#7 ·
The autotuner is wired in through the harness. Does it need a mod like the PCIII perfect install? I did that back in the day with my PCIII and had stuttering issues off idle.

Are you certain the two intake nipples abandoned by the removed LCV hoses are independently capped?
Yes. When first removing the LCV, I was really lazy and put one of the hoses between them and it ran terribly. Amature I know. I capped them separately and it is much smoother now.
 
#8 ·
A sneeze will blow off vacuum caps (backfire through the TB's).

AIS port still capped?

Check the throttle cable adjustment @ the throttle body it needs to be tight.

Insure that the throttle returns to the throttle stop. You may need to adjust the cable @ the twist grip.

Hot engine: Use WD40 + the straw, spray the intake manifold to head etc. An increase in rpm = a vacuum leak.

If all is ok set base idle it should stay where you set it. Add throttle for a minute when starting a cold engine.
 
#13 ·
If you are lugging the motor off the line then stop doing that man, this motor likes rpm's so don't baby it . . . let 'er rip!

Any time the warm idle rpm is higher than the riding rpm there's a problem, and often enough its a vacuum issue or less often its extra fresh air entering via the LCV hoses into the intake nipples (which is often offset by adjusting the warm idle rpm down). If you have zero such issues suggest you start from zero and set-up the bike for tuning. Then re-visit the PC-V.
 
#12 ·
Suggest eliminating the rolling in gear idle thing it is hard on the pistons. Beside the extended flame front issue the pistons are subjected to excessive skirt wear.
 
#14 ·
Reviving an old thread.... but did anyone ever find a fix? Having the exact same situation - I can pull the clutch in and shift to neutral approaching a stop and it will idle at ~750rpm, as soon as i come to a complete stop the idle changes to ~1000rpm. If I set the idle screw any lower its hard to start.
 
#15 ·
Often the person finally gets around to testing for vacuum leaks and doesn't post.

When inspecting, you want to know there are three air sensors, two have vacuum hoses and the third (ambient air pressure) needs to remain open to atmosphere so no vacuum hose or nipple cap.
 
#16 ·
I still have my same issue like this and have been asked about it from other members who have the same issue but more noticable. I have checked everything I can and still does it. It's not very noticeable as mine only raises about 50 Rpm's or so and it's only at the Very last foot of a complete stop. If I'm rolling with zero throttle and even in neutral it still does it to the last 1 mph. After a while I started to think it had to do with the speed sensor picking up moment and it controlling the timing (or some other sensors) just a little bit and adding fuel.

But like I said mine is not as noticeable like others.
 
#17 ·
There is a section in the manual listing and describing sensors that signal the ECU to add fuel. Plus the LCV descriptions in case a temperature sensor is signaling. Maybe we can all have a look with fresh eyes and this sequence in mind. I'm hoping to be home tomorrow.

Also, in some cars, gunk build up in the intakes after the butterflies absorbs heat and/or covers a port or sensor and creates conditions where an intake air sensor signals for more fuel when the motion sensor stops signaling motion. But I dont know if the Warrior's array would do that.

Maybe if the TPS had rough patches inside or was slightly out of adjustment but would need to read-up in the manual. I dont recall if the motion sensor interfaces at that moment.
 
#20 ·
Check cable for binding. When I had the stock airbox I had issues with the cable binding and not returning to idle fully.
 
#21 ·
Awe man, I didn't post what the fix was. <slap on hand> FWIW, I had back surgery shortly after those posts and forgot till I saw it I even had this issue.

About that time, I saw the wiring harness's terrible condition and rebuilt it. Also had to replace a BUNCH of parts for reasons. Put all new rubber on everywhere I could come up with.

The bike was down for a long time but fine once I got it going again.

I could tell you IN MY SCENARIO it was definitely not a vacuum leak or the throttle cable. Don't think* it was the TPS but did have to replace that a while back as well, just don't remember when/why. It was something electrical I think. Anyway, suggest looking at the wiring harness.
 
#22 ·
@lowriderdog37

IMO the TPS, in your scenario, was the slightly-more-likely culprit. Internal wear damage causes idle error and phantom ghosting (searching). But the high-rpm-at-warm-idle symptom can also be caused by vacuum hose or LCV system leaks. Often it's hard to prove vacuum hose integrity which is why many folks just swap them all out (as a matter of convenience and preventive maintenance). But either way I'm glad yours is golden again.
 
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