CB1100 Idle speed instability problem

[johnf514_imp]

pdedse, are you saying the high idle condition went away after the bike cooled down and was restarted?

Yes, about an hour later I started the bike and it held steady at 1000 or maybe it was 1050rpm, but I didn't ride it more. That was about 10,11 days ago but then I left for vacation and I still have another week before I return home.

I'll get it out again a week from this Saturday to see what it does.

What a fickle gremlin, this high idle.

[pdedse]

pdedse, are you saying the high idle condition went away after the bike cooled down and was restarted?

Yes, about an hour later I started the bike and it held steady at 1000 or maybe it was 1050rpm, but I didn't ride it more. That was about 10,11 days ago but then I left for vacation and I still have another week before I return home.

I'll get it out again a week from this Saturday to see what it does.

What a fickle gremlin, this high idle.

What a fickle gremlin, this high idle.
Now it has character! : )

[the Ferret]

pdedse, are you saying the high idle condition went away after the bike cooled down and was restarted?

Yes, about an hour later I started the bike and it held steady at 1000 or maybe it was 1050rpm, but I didn't ride it more. That was about 10,11 days ago but then I left for vacation and I still have another week before I return home.

I'll get it out again a week from this Saturday to see what it does.

What a fickle gremlin, this high idle.

What a fickle gremlin, this high idle.
Now it has character! : )

What a fickle gremlin, this high idle.
Now it has character! : )
[/quote]

[Magnus_imp]

So I took the bike when I went to dinner last night. About 5 miles of freeway, and three red lights (each way). The engine had plenty of time to reach operating temperature, but the idle was a perfect 1,050 RPM. This problem sure has me challenged! I'm thinking that maybe something in the way the IACV works is causing it to stick, and not function properly. Does anyone out there understand what controls the input to the IACV, and maybe how it functions? I am convinced that the engine operating temperature has something to do with it because when I unplug the Engine Oil Temperature (EOT) sensor when the idle goes to 1,500 RPM the engine returns to 1,050 RPM. Maybe the EOT sensor is sending a wrong signal to the ECU telling it that the engine is cold and therefore adjust the IACV to increase the idle speed? But I replaced the EOT sensor and this did not fix the problem. I'd replace the IACV, but another member reported that he did this and it did not correct the problem. I'm going to take it out to the desert and make another WFO run to see if this works again, as soon as I get a chance.

I wonder if there is some sort of planned obsolescence issue going on. As if something in the IACV is not designed to go beyond X miles.

My bike started this behavior around 7K mileage. Anyone else?

I think my problem started around 8k miles also.

I'm having pretty much the same problem as you as I previously posted. While the high idle seemed pretty constant for a while now it seems to come and go at will. I've kinda thrown in the towel and I'm just trying to ignore it now when it happens. Replacing the IACV was a bit of an involved job and made no difference. I replaced the EOT sensor as well.

Vey's Powersports in San Diego (El Cajon) has a new 2014 CB1100 for $5999 - maybe I should just buy a new one!

[dave]

I'm having pretty much the same problem as you as I previously posted. While the high idle seemed pretty constant for a while now it seems to come and go at will. I've kinda thrown in the towel and I'm just trying to ignore it now when it happens. Replacing the IACV was a bit of an involved job and made no difference. I replaced the EOT sensor as well.

Magnus, did you closely inspect the operation of the IACV before completing your reassembly? Is it possible the IACVs on the affected bikes are just sticking? I don't understand exactly how the IACV works. I listen carefully for it every time I turn my ignition key on and I hear it cycling. Can it make this noise that sounds like it's working but in reality it's sticking? What kind of movement of the IACV are we talking about - a few thousands of an inch, or a few tenths? I'm wondering how sensitive it is. If its total movement is only a few thousandths of an inch then maybe some slight sticking is the root cause? Does fuel run over this valve, or is it just air only? I am wondering if adding fuel injection cleaner could help (actually I have already tried this - unsuccessfully).

[MM300_imp]

I've held off posting back to this thread more than I'd originally intended to but here is the current state of my issue. As previously posted I did the throttle twist reset and it 'cured' the high idle...till about the middle of the next day. I didn't ride for a day after that and then I did the reset one more time. The bike has idled perfectly every day since. At this point I've run about half of my bottle of Lucas injector cleaner through it and I'll finish the bottle. I don't know if it did anything. The only real, immediately observable and positive effect resulted from the throttle reset.

My riding style is pretty sedate. I never speed on the bike. Since I quit commuting on it two seasons ago I probably haven't exceeded 50 mph on it. The throttle has never been worked stop to stop. Is it possible that this somehow messes with the computer? If that is in any way possible, every ride now gets at least one full throttle roll on. Maybe that will help the system to remember where 0 is and where 100 is and maybe that will help it to know where the correct idle point is. Or not.

[pdedse]

So for those with high idle issues...frustrating as it may be, are there any long term problems with just ignoring it, ride like you always do and just live with it? Anyone with high idle have stalling issues? I actually bought this bike to do long distance rides, travel the Northwest lots and across the US a couple of times.

[dave]

So for those with high idle issues...frustrating as it may be, are there any long term problems with just ignoring it, ride like you always do and just live with it? Anyone with high idle have stalling issues? I actually bought this bike to do long distance rides, travel the Northwest lots and across the US a couple of times.

My idle issues initially started with low RPM and stalling. Every now and again the idle will dip down to about 500 RPM when I put it in neutral at a stoplight, but it has been returning back to 1,050 RPM by itself. Concerning the "just live with it" approach: I HATE slamming my bike into first gear from neutral at every stoplight when it is idling at 1,500 RPM - this makes me feel like I'm riding a Harley! This can't be helping the transmission.

[Lord Popgun]

Dave, the IACV is two parts. A stepper motor connected to a slide valve (service manual term, not mine). The ECU commands the stepper motor and it rotates the slide valve.

I don't know how much it rotates. The manual says when installing, turn the slide valve clockwise until lightly seated on the IACV. The arrow showing rotation on the picture could be construed as showing around 90 degrees, but no value is listed and I do not know.

The throttle valves and IACV are upstream from the injectors. They control air. The ECU controls fuel by varying the injector dwell time bases on the TPS position and other inputs, fuel map and all that.

You can see this if you go look at your engine. The injectors are the last this before the throttle body rubber mount to the cylinder head. Cars are pretty much the same way.

[postoak_imp]

So this happens on the 2013s, 2014s, and (where available) the 2015s?

Does it happen on those bikes that have had the ECU mod done by Guhl?