CB1100 Idle speed instability problem

[Lord Popgun]

I'm not saying WaWa gas is crap, but it is cheaper around here. And their places are usually packed.

To get back to the idle problems. If running cleaner in the tank cures a person's problem, it would seem to me to be injectors (like Ferret mentioned) not IACV problems. Really, as yet there doesn't seem to be a one fix for this.

[pdedse]

Trying to figure out if type of gas has a role in this adds another variable that's difficult to gauge, but maybe reporting experiences sheds light.

I have over 9k miles on the bike; about a 1500 miles ago, I started running non-ethanol gas because I wanted to see if it improved gas mileage. I've always gotten around 45mpg city, maybe 51 on hiway, some members here report getting 50-57 consistently. I figured maybe "better gas" could help. So for 1500 miles I ran the non-ethanol (6 months?) and I think mpg did improve by 2 per gallon. Then right before my first high idle at 1500, I had to fill with regular unleaded, one tank. Did the change in gas type trigger the high idle? I would say probably just a coincidence, but really, who knows?

That's when I left the bike for 3 weeks due to travel, got home, added 4oz of seafoam--which I had used once every 4 months during the life of the bike--did the throttle reset, and the WOT numerous times. Ever since the bike sat for half an hour that day, I have had no problems with idle except maybe yesterday when after an hour plus ride, it dipped to about 850 for one stop, but then stabilized at 1000 shortly after. With this one exception, on the 6 rides since the high idle went away, the 1000rpm has been solid.

Since that one tank of regular non-leaded (87 octane?) I've used the non-ethanol only, maybe 3 tank fills. However, I'm not going to be a fanatic about using non-ethanol. Our bikes should run fine on regular non-leaded 87. In fact, I'll start running other gas now to see if I can trigger the high idle again--that would be interesting.

Bottom line for me: before the first ride after experiencing the 1500 high idle, I added 4 oz of seafoam and throttle reset while bike was cold. Then I rode WOT numerous times in gears 2-4 mainly. The idle during this one ride fluctuated between 1000-1500. Then the bike sat for 30 minutes...and no problems since.

[dave]

I've posted multiple times to this thread, so I won't go back over any history. I last reported my high idle returned when riding stop & go (mostly stop) in town, and the engine got hot. As has happened several times, the idle returned to normal (1,050 RPM) after the bike sat for roughly 45 minutes. I dumped a can of fuel injection cleaner in the tank (probably 3X the recommended amount) and my mileage went up from the low 40's to the mid/upper 40's. Coincidence? I don't know, but I calculate my fuel mileage the old fashion way, with a calculator. Rode the bike to Palm Desert yesterday - 60 miles of 70 - 80 mph freeway, followed by 60 miles of 50 - 60 mph two-lane (each way). Temperature was 110 degrees F in Palm desert. Stopped at four stoplights in town and each time the bike idled perfectly. Stopped for lunch, and restarted the bike about 40 minutes later - perfect idle. The wife didn't like the heat, so we headed home. The bike is still running perfect. So my point is, the high-temperate, slow speed riding (admittedly it was only 4 stop lights) didn't cause the high idle again. Maybe I was just lucky. Maybe the fuel injection cleaner did something? Maybe the IACV is sticking, and over time it is freeing itself up? I still believe the high idle is somehow linked to the IACV, whether it is the valve itself, of the signal it receives from the ECU. To be continued.

[curlyjoe_imp]

Dave, I'm pleased that your CB is idling normally these days and my fingers are crossed in the hopes that your fortunes continue.

I think there is merit in using top tier fuel with detergents and adding products like seafoam or injector cleaner periodically to keep the entire fuel system nice and clean. So the question I have is how does "gunk" accumulate in the IACV to keep the valve from operating reliably? Certainly johnf514 had an electronics issue in the IACV that was solved by replacing the part. Does a sticking IACV mean that deposits that accumulate over time prevent the valve from operating reliably? Initially I thought that the IACV only sees filtered air and that deposits shouldn't accumulate over time. After going through the service manual, I realized that our CBs have a crankcase emissions system (page 1-31 in the 2103 service manual). There is a crankcase breather hose running from the top of the engine to the front airbox. This system distributes blow by gas and presumably other nasty vapors from the crankcase back to the front airbox and then through the throttle body for combustion. Presumably the IACV is exposed to these crankcase emissions when the bike is idling.

If the blow by gas is composed of top tier fuel with detergents and fuel additives, is it possible that the IACV and throttle body is kept clean and functioning properly?

disclaimer: I'm not a mechanic so I'm just speculating with the thought of trying to help out.

[DaSwami_imp]

Recycling engine blow-by gasses back into the intake may help the environment/emissions, but is lousy for the engine. Just ask any owner of a diesel pickup built in the last few years....

[dave]

Thanks curleyjoe. I understand that the IACV is not subjected to fuel, but the valve itself (it's electro-mechanical) could be sticking. Also, the valve could be sticking in the throttle body interface due to an imperfect fit. I can understand how a sticking valve can cause symptoms that come and go, but I don't understand how unplugging my EOT sensor suddenly makes the bike run perfect. Maybe unplugging the EOT sensor causes a completely different signal to be sent to the IACV that forces the IACV to react in a way that cures the unstable idle speed? Maybe this forces the IACV to go into a fully closed or fully open position that overrides a sticking condition? I have always used top-tier, 91 octane fuel in my bike, but that doesn't mean I didn't get some bad gas at one time. I wish I had more feedback concerning the effect on the high RPM idle when unplugging the EOT sensor. I believe somebody posted that replacing their EOT sensor cured the problem - replacing mine did not. To be continued.

Recycling engine blow-by gasses back into the intake may help the environment/emissions, but is lousy for the engine. Just ask any owner of a diesel pickup built in the last few years....

VW diesels had an issue with this in the early eighties. The blow-by gasses caused the engines to accelerate unexpectedly.

[Mechanix_imp]

I guess I'll hop on the wagon.

2014 Standard, ~5000 miles,
K&N, Yoshi RSCV, Power Commander V

Idles fine at start up. After riding long enough to heat up, when i come to a stop/light the idle seems to be searching. It will drop to ~800, then climb back up to ~1050, then drop back to ~800, etc. It hasn't stalled at all, and responds normally to throttle input. It's never done the 1500 jump that others seem to have experienced.

Suggestions?

I'll jump back on too. My issue went away for a while but has come back to annoy me even more.

I don't have the hi/low idle, just low idle that creeps back up to normal. Now on every ride it will drop idle to about 500-700 and creep up, it has only shut off on me twice. I have taken some video to show the service techs so they don't think I am trying to BS them.

I'm only at about 6,000 miles and I first noticed it at 500 miles but it was only once in a while. Now happens every ride, but goes away for a while if I shut it down and restart it. Gas, temperature, riding style, or distance don't seem to be a factor. I love the bike but am not happy reading about the issues with no resolution from Honda.

Sorry for the small rant, just had to vent a little bit.

[kennyw]

Thanks curleyjoe. I understand that the IACV is not subjected to fuel, but the valve itself (it's electro-mechanical) could be sticking. Also, the valve could be sticking in the throttle body interface due to an imperfect fit. I can understand how a sticking valve can cause symptoms that come and go, but I don't understand how unplugging my EOT sensor suddenly makes the bike run perfect. Maybe unplugging the EOT sensor causes a completely different signal to be sent to the IACV that forces the IACV to react in a way that cures the unstable idle speed? Maybe this forces the IACV to go into a fully closed or fully open position that overrides a sticking condition? I have always used top-tier, 91 octane fuel in my bike, but that doesn't mean I didn't get some bad gas at one time. I wish I had more feedback concerning the effect on the high RPM idle when unplugging the EOT sensor. I believe somebody posted that replacing their EOT sensor cured the problem - replacing mine did not. To be continued.

Recycling engine blow-by gasses back into the intake may help the environment/emissions, but is lousy for the engine. Just ask any owner of a diesel pickup built in the last few years....

VW diesels had an issue with this in the early eighties. The blow-by gasses caused the engines to accelerate unexpectedly.

My guess is you are triggering a limp mode by unplugging a sensor input that the computer needs. Limp modes do not automatically try to adjust on the fly. However, that is pure speculation as i have not studied the system.

[pdedse]

Well, not sure what to think...haven't had any issues with the bike till today. Went for a 90 mile ride late afternoon with 90+ temp through rolling hills, not many stops, idle fine till about 1.5 hours into the ride. Stopped to get something to drink and the idle fell to about 550-600 and bike seemed as if it were going to die, but didn't. I have not had this issue, only the high idle. I let the bike idle and watched as the needle slowly crept back up to 1000, where it stayed. I let the bike cool for half an hour. Did the throttle reset sequence. Bike idle was right at 1000. Rode another half hour home where idle again dipped to 550, but rose to 1000 in less than 5 seconds and it idled fine at that point. Not sure if that happens for others at any time, but it's (the low idle) the first time it happened for me. Bike runs fine otherwise, no high idle.

[Riko_imp]

Have you blipped the trottle while it was at low idle?

Thats when it could stall...