CB1100 Idle speed instability problem

[peterbaron]

IMHO the best in fixing problems is, if I count on myself. One diagnose, one repair, one fix, ONE person responsibility... and NO-one complaints. Period.

Worked 4 decades for car dealerships (same make)...50% mechanics are butchers/parts replacers, a few techs are OK, generally, each dealer has one good, honest and profesional hi-tech trouble-shooter.
If you have a good car and bad mechanic = he will ruin your car...you dont even know how bad diags I've seen, horrors....multi ATM +++ replacement (one car) for misdiagnosed/loose ground bolt.....and the butchers get the best/easy jobs, and you cannot get rid of them
If you have a problem vehicle and good tech = he will fix it for you.
My advice: find good tech and stick with him/establish good relation as long as you can..., he will tell you what you need first, what last, and what is not needed at all, no substitute..

Needless to say, this forum is fortunate by having good techs/people
Good luck to all.

[SportsterDoc]

For the record, so that a rant does not overlay the diagnosis and solutions posted on this thread, post 1159 is one of the summaries and the issue is NOT the fuel injection system, it is the idle air control valve with only a couple exceptions, such as a damaged TPS wire.

It is most unfortunate that there have been issues, no matter how small a percentage, but through joint efforts on this forum, the major cause has been identified.

I put over 12,500 miles on my 2014 standard, in 10 months, with ZERO issues.

[curlyjoe]

Cormanus or Ferret, can you help speed out with the spreadsheet?

I’m not sure Popgun. I just tried to load the spreadsheet and it told me my permissions had been changed and I could not access the document. That’s likely to mean that whoever created it—Max, maybe—needs to update the permissions and post a new link.

I’m not sure Popgun. I just tried to load the spreadsheet and it told me my permissions had been changed and I could not access the document. That’s likely to mean that whoever created it—Max, maybe—needs to update the permissions and post a new link.
Hi guys,

Sorry it's been awhile since I dropped by. Can you access the spreadsheet now?

https://docs.google.com/spreadsheets/d/1...edit#gid=0

EDIT: After some detective work, someone else took ownership (anonymous leopard) of the original spreadsheet link here:

http://www.cb1100forum.com/forum/showthr...?tid=11247

[max]

Thanks curlyjoe, i have downloaded it in 3 different formats just to be sure to be sure. good job.

[syncronizator_imp]

My Idle problem seems to be solved until now.
I have traveled 12000km since replacing the IACV.
The problem never recurred.

[Cormanus]

Good news, synchronizator.

[max]

Thanks sync, that's great news, thank you for all the effort you put into this thread and this feedback, all the best to you.

[SportsterDoc]

Glad to see multiple confirmations of the team testing that was done two and a half years ago reference post 775:
[url=http://cb1100forum.com/forum/showthread.php?tid=8120&page=78]http://cb1100forum.com/forum/showthread....20&page=78

[iamheero_imp]

Hello all,

It's with a heavy heart I write this comment but I'm at my wit's end trying to tackle this solo so far! I believe my 2017 has been afflicted by this nasty IACV issue and it's a real bummer, but it's taken a long time to diagnose because of how intermittent it is. I had put about 22,000 miles on the bike before I had the valves adjusted (not that I noticed any issues, but I felt like it was overdue). While I had that done, I also got my bike professionally tuned by a local shop with a good reputation. Although it rode fine for a while after, things have gotten progressively worse and I think I'm going to have to take the bike in soon.

First, I had very intermittently had issues with high idle as I started the bike (~1800rpm) until it was warmed up, and those were solved with a kill-switch reset. I paid it no mind, really, since it happened like 3 times over the year I was riding it and solved itself generally.

Then I started noticing it would stay above ~1100 rpm even after it should have warmed up and this happened frequently.

THEN I noticed that the RPM would drop to 5-600rpm at idle, rolling up to stop signs and in traffic, and unless I rolled on the throttle immediately, it would die. It would start right up on me, but would die at the next stop sign.

At this point, I tried to remedy the issue myself. I changed the oil and filter early (usually at 5,000mi), spark plugs, cleaned the air filter, cleaned the TPS sensor and checked for kinks, reset the TPS, and while I was at it changed the brake and clutch fluids and replaced the chain and sprockets. I also tried to give it the ol' Italian tune-up, riding with very high RPMs and redlining it for a bit. I tried to seafoam the oil and gas and emptied and refilled the gas tank as well. I tried a tank of 93 instead of the usual regular I use. I would test after each of those fixes and was still having trouble, but eventually it just sorta stopped happening.

The idle at start was high, 14-1500 until warm, but after about 10 minutes of riding it would settle at around 9500 and was *fairly* stable. Less stable than I was used to before all this, and not reading where it should, but it got me around town and felt great when I was in motion. And for about 1000 miles it didn't die on me again, but the weather was getting cooler too at this point and I hear ambient temperature could affect the IACV issues.

So yesterday it was a warm LA day and I went for a ride, it died on me a few times in traffic. Same 600rpm to stall pattern as before.

So the question I have is this: does this sound like IACV troubles? Anything else I can do? Money isn't exactly flowing like water with COVID so if I could avoid giving a shop several thousand dollars to fix a highly intermittent and difficult-to-diagnose problem that'd be great.

[max]

Iamheero thanks for your very detailed response, you are the very first one with a 2017 model with this issue, i find it interesting that the bike was "serviced" shortly before these things happened.

As a first response i would have a very careful talk with the actual tech who did the service and without letting him know you have this problem try to find out what exactly he touched or worked on.
I agree that the symptoms are similar but cannot help thinking something happened during the service and i am glad you mentioned it.
As the group discovered various sensors have an effect on the iacv response, the engine temp sensor for instance can put it way off and does not set a mil code from memory if disconnected.

My first response would be a connector that is not seating properly or a pinched wire but that is just a guess and just for kicks have you had a close look if any vacuum hoses are loose/missing/damaged/ not in the right place etc?.

And as an interim measure you could disconnect the iacv when it idles correctly warmed up, it won't set any codes and is very likely to stay in that position, just unsure of how it idles when cold but you can always open the throttle manually on startup, my honda 900 hornet only has a manual adjustment screw and it always starts fine with just a little help from the throttle handle.

All the iacv does is pass air through the throttle bodies for the engine to startup and idle which is the same as the old fashioned idle adjustment screw on a set of carbs, the temp sensor will do the correct fueling for the engine at all times.

I also hope other members who have had iacv issues will check in and verify your diagnosis and/or ask for some more details before advising something.

This fault is very difficult to pinpoint for a tech unless he had a lot of experience with these cases and you could be led in the wrong direction by someone with less experience.

Bflint is in the San Diego area and has access to the diagnostic device to check iacv steps and other sensors, that may be useful at some stage.

So at this at this stage just gather some evidence and possibly we can find an answer if we put our minds together for you