CB1100 Idle speed instability problem

[Speed_imp]

After another 15 Km test drive with start stop driving the issue has not come back after replacing IACV. Before it was quite easy to reproduce the fault even without driving, just some throttle openings in a row and idle speed was lowering till stall, as time and kilometers passed by the syndrome was more and more evident and acute so at this point I can say the IACV replacement solved my low idle issues. Thanks to all the people helping; Popgun, Dave, Max, Pawel and all the others I am forgetting to say!! I would like to add this case to the spreadsheet but I don't have access.

[Lord Popgun]

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

[peterbaron]

Speed and LP, is this the spreadsheet you are looking for?:

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

[dave]

Hi Guys, somewhere in the previous 117 pages on this topic my question may have been answered, and I apologize if it has: I am curious if anyone has had a defective IACV correctly diagnosed and repaired by a dealer, and if you did, how much did the total repairs cost?

Thank you.

[pdedse]

Hi Guys, somewhere in the previous 117 pages on this topic my question may have been answered, and I apologize if it has: I am curious if anyone has had a defective IACV correctly diagnosed and repaired by a dealer, and if you did, how much did the total repairs cost?

Thank you.

I'm going on memory Dave, but I think either someone here said $1,300-1,400, or maybe it was my dealership that said that given an "if" scenario, but I didn't go that route.

[Lord Popgun]

If they go by the service manual they aren’t going to find anything wrong with the IACV and they say you need an ECU. Even if it is the IACV. Which it has been every time now IIRC.

[max]

Thanks for the video Pawel and very good of you to be patient with the iacv to see what is happening rather than opening the throttle and thereby changing what actually happens, good work, it initially appears that nothing is going on but it slowly falls into place, something to note is that the iacv opens with left-hand rotation and closes with right-hand rotation of the shaft which i found out in slow motion.

And opening the throttle produces a right-hand motion if the shutter speed does not fool me in slow motion and closes the throttle.

A lot of people would find this boring but i find it fascinating to see what happens and when, it supports what i have been constructing in my mind about what happens but does not answer all questions, on opening the throttle the piston closes the idle air, but we all know that the engine is trying to keep it from stalling, you can feel it, so why does the iacv do the opposite of what i would expect? i can now watch all assorted video's and work things out over time.

Initially it seems that the rotor has enough force to motivate the piston provided there is enough energy ( time ) to make that happen.

Sofar i think two things could be the cause;
1 the iacv pin is too long and is trying to interfere with the piston who is trying to stay in the center of the barrel, the rounded tip is wearing flat over time and produces more friction or
2 the change in the software for the 2014 model has a functin that affects the iacv, i just have a problem with how that increases the behaviour over time?

It would be cool to get the old iacv out, file the pin shorter by a fraction, clean out the swarf and put the same iacv back in for a trouble free ride.

Thanks for all the effort Pawel, i now have more bits of the puzzle to let my subconscious mind work on it.

[Speed_imp]

Another idea that comes to my mind Max is that the spool is made by two pieces:

- External or outer body (silver)
- Internal hub with the thread (golden)



If you force it you can make both parts slip in reference to the other with not much effort, so if it closes the valve and the spool goes to end of travel making phisical contact with the housing and the axle keeps on turning (if it has enough force to do it) it will probably loose the real position of the spool. It can produce a wrong positioning of the valve and probably a wrong fuel mixture. Actually when it starts failing every time you open throttle the idle speed goes lower and lower. Then if you set ignition off and on again it gets again the real position of the valve and idle speed goes to normal again. Pawel can check that with his own hands to check the force needed to make it slip. Just screw to the end the spool and once at the end try to keep on turning.

Actually I have been making slip the inner and outer parts with my hands with minimal effort when screwing clockwise the spool over the axle. I mean when you have screwed it till the end and supposedly you can not turn it further in that direction.

[Cormanus]

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.

[max]

Suppose it's the "curly joe" spreadsheet since mine is still available, i do have an updated copy of my s sheet but forgot to make a copy of cj's one, it gives me the same message as previous posters so i'm stuck with that one as well, don't suppose any body else has a backup copy?

Did notice that despite the fact that i gave the valve ssheet general permission the "cloud" keeps reverting to for me to sign in again so i just grab new details and fill them in as requested, it still seems available to be viewed though.