CB1100 Idle speed instability problem

[Cormanus]

Would one of our experts likely to offer an opinion about whether it is likely there is more than one cause of this problem?

[1973cb750]

Would one of our experts likely to offer an opinion about whether it is likely there is more than one cause of this problem?

I'm not saying ECU is only colprit but 75% of time probably is doesn't mead other things like the iac don't fail too but if it's the a23 theirs a good chance that's the problem

[GoldOxide_imp]

It's been 2.5 years since I replaced the IACV on my 2014EX and I've had no more low idle issues.

Sounds like a fair empirical data point.

[Lord Popgun]

Cormanus,

It seems like at first changing the IACV fixed the majority of problems although we could never find a real reason the IACV wasn't working properly. Then we found out that there was a software fix in Europe that Honda North America refused to admit existed but cured problems in Europe. Then the A24 ECU pops up and is fixing problems and is, pretty much no doubt, programmed with the new software or an internal hardware improvement.

Honda has not been any help on this, but my opinion is it is either the ECU or IACV and is hard to tell exactly which is the bad actor. Pay your money and take your chances I guess. But first reseat/clean all connectors, etc. Basic stuff first.

Max, Powerdubs, and SportsterDoc may have more input.

[peterbaron]

.....generally speaking many but not all electrical problems are related to poor contact or resetting electronic modules such as ECU, TCU, ABS/ESC/TC, 4/AWD+++... and the person working on his/her bike/car before replacing a possibly "bad" component must disconnect some related and unrelated electrical connectors that had poor contact, unknowingly fixing a "poor contact problem" and thinking it was a component...it can be tricky and confusing.
We are fortunate that motorcycles are not as complicated as cars which have many more e-modules, C low-high-M-P-D-K CAN network where one poor contact or failed component can set up multiple DTCs preventing some e-modules from communicating during initial diagnosis, causing errors and confusion.

[Nachodaddy]

Lord Popgun has summarized it very nicely. What convinced me to take the plunge and replace the ECU was the post from a Forum member in South Korea with the problem and, when he took it to the dealer, they changed the ECU and it solved his problem. Since I had already thrown good money at the IACV, this would be my last straw. If that didn't work I was getting rid of the bike.
Happy to say, it did work. I hope it is the answer for others with the problem.

[max]

Have been quiet since there was a good set of advice available from different members and too many cooks spoil the broth.
But Cormanus asked for our opinion so here it is;

Popgun and all have been trying to get to the best solution we can come up with, none of us have this issue so we had to rely on others reporting and finding a way to solve this issue, the first fix from the dealer was to replace the entire throttle body, we then thought that just replacing the iacv was a better solution and it worked for several members, international members had their ecu updated by the dealer and permanently fixed the problem but the us has not made this option available.

Recently the ecu replacement has had the desired effect, the fact that the majority of faults have been in the 2014 models points straight to the ecu.

But another point started to take shape in my opinion; one thing that also happens when replacing the iacv is that the battery is disconnected for some time which made me wonder;
Is it possible that the ecu has reset itself to an original state as if it has left the factory by disconnecting the battery which discharged the capacitors inside the ecu which also supply some part of the memory....................................
Keeping in mind that the ecu has performed fine until the issue started.
Because i have no practical experience with these cpu resets i asked Peter B ( who does have some experience professionally ) in a recent email and he responded that it is a POSSIBILITY in some ecu's.

So has the replacement of the iacv whilst disconnecting the battery ( which could be the key operation ) fixed this??

I think it is at least worth trying to disconnect the NEGATIVE terminal of the battery AND connecting it to the still connected positive terminal ( perfectly safe to do it this way ) thereby discharging the ecu capacitors for an hour or so and see if doing so changes the behavior of the bike.

The ecu memory consumes a minuscule amount of power so it takes time to " sink " all electrons inside the ecu to ground and erase the memory.

So in conclusion the ecu which is now available does fix this problem @ 500.00 us but it may be worth investigating if the battery reset also works for no dollars for some period and then can be repeated if the situation requires it and helps other future members, at this stage we simply don't know!.

Not a short reply but worth a try i think,

up to you.

[Nachodaddy]

Max, I did try that and it worked . . . for awhile. I was given the impression by some who know these things a lot better than I, that I was simply erasing a code and not fixing the problem that set the code. I would dis-connect my battery cables from the battery and connect them together for 15 minutes (or more) and then, when I reconnected the battery, the high idle was gone. But, after awhile, it would slowly start creeping back in. But, I was so excited about it, at first, that I was certain that was the solution. For someone who doesn't mind doing it, it will work and maybe for a longer time for someone.

[Cormanus]

Thank you gentlemen.

[Enzofour_imp]

It's been 2.5 years since I replaced the IACV on my 2014EX and I've had no more low idle issues.

Right after I replaced the IACV, the dealership uploaded a patch to my ECU that he'd gotten from Honda since 2014.
So I don't know which of the two fixed the problem.