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+--- Thread: Really high idle (/showthread.php?tid=4483)
Really high idle - Gordo_imp - 09-12-2021
Today was the Cpl Humberto Sanchez escort ride from Grissom AFB to the funeral home. I'm setting this as the back drop. Temps were in the 90's and then procession was slow. Alot of 1st and 2nd gear riding in the heat. I noticed my idol was low during the ride. After the pass at the funeral home we ran a pretty spirited ride thru Logansport to Wabash. The bike then died at the light when I was taking off to make a left turn. It eventually fired and I parked it for an hour while we ate. It sat for an hour and when I fired it up the idol was was between 1700 and 1800rpms. I rode the bike home like that for 45 miles. Any ideas? I'm at a loss. No mods to the engine, stock air filter, Yosi exhaust with the quiet baffle removed.
Titus 2:13
2013 HONDA CB1100
RE: Really high idle - Lord Popgun - 09-12-2021
I would suspect the IACV
Really high idle - Gordo_imp - 09-12-2021
What exactly is that?? Something I have never heard of.
Titus 2:13
2013 HONDA CB1100
Never mind.....just looked it up. Thanks for the reply!!
Titus 2:13
2013 HONDA CB1100
RE: Really high idle - Lord Popgun - 09-12-2021
Idle Air Control Valve
Mounted on the air plenum and controls idle speed. It is a stepper motor that drives a valve and is commanded by the ECU.
Max will most likely chime in on this. We have a BIG thread on just this problem. If this is your problem, it won’t be fun to change.
http://cb1100forum.com/forum/showthread.php?tid=8120
Really high idle - Gordo_imp - 09-12-2021
Hoping and praying it's not. I'm actually reading that post now.
Titus 2:13
2013 HONDA CB1100
RE: Really high idle - max - 09-12-2021
Hi Gordo, this valve regulates the air which bypasses the four butterfly vaves from the throttle.
It is the modern replacement of the idle adjustment screw on normal carburettors and normally works very well as you know.
What you describe is the classic situation in which it fails, my guess is that the permanent magnets inside the stepper motor lose their magnetism because of the heat and thereby the ability to operate as before.
There is also a flaw in the duty cycle ( i think ) of the software inside the ecu that does not appear in other models, the 2014 models seem to be affected the most with this situation as you probably have worked out.
Look out for some info towards the end of the thread, there is a more convenient way to replace the iacv.
Nobody has found a difference between the old and replacement iacv, not drag or anything else hence my theory of the weakened permanent magnets due to heat.
This valve operates regularly when the bike is moving, not just when it is idling.
As a positive point no iacv replacement has had any more problems
RE: Really high idle - Henrik_imp - 09-12-2021
I have read all the posts on this issue before, and there are a lot, and although I do experience the same problem from time to time I have not yet done anything radical to fix it.
Since the problem for me is really intermittent, what I do when it happens is that I switch off the engine with the kill switch. Then I will open the throttle fully a couple of times, switch the kill switch back on and start the engine. After this, it has then begun working fine again. I believe the action of switching off the kill switch and opening the throttle does some sort of reset. I am pretty sure this has been mentioned on one of the many threads on the idle topic.
For sure, it does not fix the problem permanently as it then may happen again from time to time, but it has always fixed the problem for that specific ride. Something simple to try perhaps.
Really high idle - Gordo_imp - 09-12-2021
You guys are awesome!! Thank you all for the tips and info!! I really appreciate the help thru this.
Titus 2:13
2013 HONDA CB1100
RE: Really high idle - max - 09-12-2021
Thanks for the tip Henrik, as you would have read; on every startup the ecu does not know at which position the iacv is, so it "resets" the iacv fully open and then steps it back the amount required to idle the engine at the temperature it is at that time.
You can experience this when you start the engine when this cycle is still in progress and the engine revs higher before settling down at the appropriate rev's for it's temperature.
If you have the diagnostic tool you can also observe the position of the iacv, the program indicates the position as a number in the data list and you can see it change for every "step" as the ecu adjusts it's position.
It also moves when you operate the throttle from closed as some type of "takeoff assist".
RE: Really high idle - furious_blue_imp - 09-13-2021
Probably not relevant here but I'll mention it.
My long gone Harley Softail was programmed to kick into high idle if the oil temperature got above a preset limit. The idea is that with the engine on the brink of overheating they want oil circulating faster to cool the engine. Given that I'm sure that they've tested this thoroughly and it works as an emergency measure, it kind of surprised me to read about this in the manual because I would have just assumed that higher rpms automatically meant higher temps, but then this is the idle speed and the engine isn't running under a real load when this happens so I guess it makes sense. It had happened to me a few times on that bike and once traffic got moving and the engine cooled down the idle speed would go back to normal.