CB1100 Idle speed instability problem

[peterbaron]

Hello ALL CB owners,
.....idle speed fluctuation (when fully warmed up)....maybe this maybe that, dealer replaced few parts without any results.. :(

If part is defective = needs replacement. If needs ECM/software reprogramming = YES must go for it.
But let's say your idle is erratic even if ALL components are NOT defective, ECU has the LATEST version, no DTC present, electrical connectors are sound, your bike has NO!!!! mickey-mouse ECU related aftermarket gizmos/modifications, throttle cables are not sticky and are adjusted properly as well as the th. plates, crankcase breather + other one are already cleaned out....what you MAY do next....

ISC or IACV does similar if not identical job in FI system= control idle (through air flow, not fuel) when throttle is closed .
Your throttle plate is closed and its voltage reading is being sent to ECU through TPS . ECU calculates its value ( and other values as well, like engine temperature , injection time, ignition timing.. etc) and continuously tells ISC/IACV to be open more or less to maintain proper idle .
I would check ( as ONE of possibilities) if throttle plate has excessive carbon build up, which prevents throttle plate to go to full closed position and as a result , TPS sends erratic signal to ECM which as a controller sends command to ISC/IACV to open-close-open....++++ and you get idle fluctuation.
In a less likely scenario ISC/IACV , intake valves may have carbon build up as well.

To check your throttle is not going to be so easy due to limited space access but it can be done...and make SURE you check your throttle body when plates are FULLY OPEN.
For my '13 CB with 42K, I regularly use fuel injection cleaner ( to gas tank) 2x a year when gas tank is full and oil /filter change due, drive my bike to empty tank and replace oil/filter = done.
For winter storage , I add FI cleaner (proper amount to fuel volume) when engine is still warm, idle it for a while, turn ignition off and park my bike for winter hibernation.
I always use highest octane rating available at the pump (usually 94 or 92)...'cuz it is LESS dirty than regular ( has less ppm)... I don't even know and care what octane rating owners manual recommends to use.
THIS IS WHAT I DO WITH MY LOVELY CB1100A... you may follow or not, it depends entirely up to you.
I do NOT intend to overwrite service manuals or provide field fix but only a THOUGHT.
All vehicles require regular maintenance as per manufacturer's manual = read yours, please.

Cheers to ALL
Peter
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'13 CB, 42K

[dave]

[quote='Magnus' pid='172656' dateline='1495831855']
So... still having the 1500rpm idle problem. I've tried all sorts of things... replacing the EOT, IACV, adjusting the throttle... no luck.

So I tried UNPLUGGING the EOT sensor as some have suggested and the bike won't even start. Just stumbles and dies immediately. Strange it works for others? Are you unplugging it after the bike is warm?

Hi Magnus. I unplugged my EOT sensor after the engine was completely warmed up. I pulled off the road when the high-speed idle condition reared its ugly head, turned off the engine and unplugged it. When I restarted it the bike ran better than new. I repeated this experiment three times, each time with the same results. I would reattach the EOT sensor when I put the bike away after riding, but one time I left it unplugged. When I started it the next day it did not start cleanly, like it normally does, and it stalled. I immediately plugged the EOT sensor back in and this cured the problem.

[Lord Popgun]

Cured the idle problem?

[Cormanus]

More likely the bad start, stall problem, popgun.

[dsan1964_imp]

My bike was acting up last night idling at 1300 I turned it on and off did the throttle reset oddly enough when I got home and went right back down to 1000 but it was acting up for about an hour


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[Wisedrum]

Over long periods of time the high idle problem of my CB dispappears. I did'nt do the throttle calibration any more, it start's to become neurotic without any real change of this so to day misfunction. If it reoccurs, which it sometimes does, don't know why although I have my presumptions, I choose an empty straight street, put in the 2. gear and ride the CB full throttle for a short time.
Mostly this will cure the Honda for the upcoming rides.
I don't really like doing so, 'cause I prefer the smooth and low to mid rev riding. But if it's the only thing that helps somehow, I do so once in a while. The Honda despite of this runs well, no other bad items. Good throttle response, good, low fuel consumption. I presume this sometimes high idleing is part of the CB and all its sensors and the kat as a honda engenieer told me, to calm down my worried mind.

Wisedrum

[dave]

More likely the bad start, stall problem, popgun.

You are correct Cormanus, the starting problem.

[Rolls_imp]

My idle acted up a bit again for a day and then fixed itself. After a 55 mile early morning ride from Belmont to Soquel, I next headed a couple miles done the coast to Capitola. On the way, the bike started to stumble and idle rough or even cut out if I didn't goose it a bit to keep it alive. This has previously been a harbinger of the high idle problem, but this time it just fixed itself later the same day. Couple weeks now and no problem.

[Aka Tsubasa_imp]

Has anyone ever verified proper fuel pressure or looked for a dirty in tank fuel filter? Low fuel pressure at idle when charging system voltage is lowest might send the FI system hunting. There is a low probability of occurence but it would be good to rule out any fuel delivery variances. It was one of the first steps in proper engine diagnostics when I was a tech.

[beardyweirdy@me.com_imp]

I'm coming round to excepting that it's just one of those peculiarities of the model.
It's not the end of the world and it doesn't seem to be getting worse or causing any major failings.
It'll be interesting to see if any of the 2017 models display the problem.

I've just bought some Lucas Injector Cleaner. Thinking it's so intermittent it could just be build up of fuel deposits. It does seem that without exception turning off then on again always seems to cure it. On start up, the IACV cycles open to close and the fuel pump cycles, I'm guessing building up the right pressure.

Could be this cycling dislodges what ever was causing the issue. Likewise it could be recalibrating a component and curing it that way.

We may never know, so I'm living with it. The bike has many more positives and this is almost the only negative for me, so worth it I reckon.

The Romans used to build known imperfections into their mosaics, as perfection was the prerogative of the gods. I like to think Honda were thinking along those lines when they built in the wonky valve timing but surely not this! It's one way to mentally deal with it ;-)