CB1100 Idle speed instability problem

[Jfro5687_imp]

Just caught up on the last few pages. Forum troll? Reminded me of pretty much any social media platform of late, angry shouty rants that achieve nothing. Just tries to upset otherwise happy people. I don't read or look at it any more and if I happen across it. turn off.

[pdedse]

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.

To clarify:

1) valves were actually adjusted or just checked? Not sure if that would matter, but curious

2) was the shop that adjusted the valves the same that did the professional tuning? Sounds like it, but just to confirm

3) what did the professional tuning involve?

4) and there was no hint of high / low idle issue before valve adjustment / tuning, correct?

My '14 standard (I no longer have it) started with high idle and then low idle developed a few months afterwards. High idle: would stay at 1700-1800rpm after warming up. Low idle would happen after an hour of riding and then coming to stop, sputter at 550-600 rpm and then creep up to maybe 700. Only died twice, possibly because I knew it was coming and gave it a bit of gas. Some trips I would start with high idle and then finish with low.

All the above was intermittent. Some days I wouldn't have any issues, but most days I did. Anyway, that was the behavior of mine so that you can compare.

[iamheero_imp]

Hi Pdedse,

1) The valves were adjusted! I asked for the actual measurements but when I turned up they just handed over the bike and I was so excited to ride I forgot to get them.

2) The shop that did the valves did the tuning.

3) The tuning was on a dyno and adjusting a Power Commander 5

4) There was SOME hint of it, but it never died before that happened. I had a couple instances where the idle was higher than normal, but nothing lower until after this service.



@Max: I would be interested in bypassing the IACV by disconnecting it after it's warmed up, I have a general idea of where the IACV is but thought it was inaccessible without removing a lot of plastic behind the throttle body assembly? My first instinct was to take it back to the same shop and have them check for vacuum issues. The problem with my setup is it's a very dark apartment garage, no place to actually remove the tank or get any serious work done unfortunately! The previous maintenance I mentioned was all done on the side of the road in front of my building.

[max]

Just disconnected the iacv before starting the bike, the normal rpm is1050 and the bike started immediately and idled at 850 rpm quite happy.
The ambient temperature here is 22deg c and the check engine light did come on and blinked to indicate it had set a code, upon shutting the engine down, re-connecting the iacv connector and re starting everything was back to normal, no cel and revs at 1500.

The tank has to be unbolted with a 12 mm spanner on the rear end after removing the seat and lifted 1,5 inches in my case with a piece of wood under the tank to gain access to the plastic ( push pin type) phillips screw on the right hand side of the picture which then allows the black plastic cover to hinge forward and come off the two position tabs on the bottom of the cover;





The cover can then be removed and the iacv cable disconnected by pushing on the locking tab on the left side of the connector and pulling the connector up;



Here is the 4 pole connector unplugged by pushing the locking tab on the left, it may be possible to insert two resistors in the connector to stop the cel light coming on;



So it can be done with the proviso's mentioned and provide you with some time to evaluate the situation and possibly make another video on yt so we get a better idea.

[iamheero_imp]

@Max: That seems very doable. To be clear, is the idea to do that after the bike is warmed up and running or before you start it up with a cold engine block? I might even be able to get in and do a before/after video tomorrow.

[max]

Exactly, when the desired rpm is achieved ( warmed up ) shut the key off, the iacv will remain in that position until the key is turned on ( because you disconnected the power from the e.c.u. ) and the iacv etc. initiates the bike with a new position.

So to be clear; 1100 rpm, shut the KEY off and disconnect the iacv, done.

[pdedse]

Hi Pdedse,

1) The valves were adjusted! I asked for the actual measurements but when I turned up they just handed over the bike and I was so excited to ride I forgot to get them.

2) The shop that did the valves did the tuning.

3) The tuning was on a dyno and adjusting a Power Commander 5

4) There was SOME hint of it, but it never died before that happened. I had a couple instances where the idle was higher than normal, but nothing lower until after this service.



@Max: I would be interested in bypassing the IACV by disconnecting it after it's warmed up, I have a general idea of where the IACV is but thought it was inaccessible without removing a lot of plastic behind the throttle body assembly? My first instinct was to take it back to the same shop and have them check for vacuum issues. The problem with my setup is it's a very dark apartment garage, no place to actually remove the tank or get any serious work done unfortunately! The previous maintenance I mentioned was all done on the side of the road in front of my building.

Darn, I was hoping that your bike would have exhibited no signs of hi/low idle before the work done on your bike, because then you could have more readily suspected something happened when they worked on it.

The fact that you did have some hi idle before any work done could mean that '17ex IACVs may be susceptible to "issues" like was the case for a number of pre '17s. This would be unfortunate if true because I believe the part numbers are different for '17 IACV and those of earlier years--the hope was that Honda realized something was wrong and made a change to rectify the problem. That is speculation from comments made here in the forums.

The low idle only happened once you got the bike back, so you might think that this developed as a result of work done. And that may be the case. Yet, that was my progressively worse pattern over time on my '14 standar and no work was done on my bike between hi and low idle issues...meaning your low idle could be unrelated to valve adjustment and the tuneup you described.

My bike hi/low idle issue history if I remember right, problem started at around 10k miles:

July: first sign of high idle, 17-1800 rpm; hot day, ocurred right after filling up for gas--I mention this because a couple others reported the same.
August: intermittent high idle, usually starting a few miles after warming up
September: tried many of the things you mentioned, some seemed to work, meaning that the issue went away for a few rides, then came back
October: first low idle issue, back and forth between low and high
November: same as October, but less frequent problems maybe cooler temps? At some point disconnect and reconnect TCI (was that it?) seemed to make the problem go away, maybe 5 rides with no issues.
December: traded the bike in for a Street Twin--was on my "some day" list and they had a great price and they gave me a decent trade in on the CB1100.

Fast forward...missed the CB1100 more than I liked the Street Twin, timing was right because of a good price on a leftover '17, found a buyer for the Triumph, didn't lose too much, and I moved on. Now at 11k miles, my '17ex has been perfect...so admittedly, I was really hoping for no news of '17s having issues.

Hopefully, you will find a solution that doesn't involve replacing the IACV.

[dave]

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.

I was one of the first on this forum to experience the idle issues. My bike exhibited ALL of the identical symptoms listed by the numerous posts throughout this thread. I had my bike back to the shop, and contacted Honda customer service directly, where they provided totally unacceptable (lack of) support, that I will not get into here because I posted all of this information previously.

Just wanted to confirm that replacing the IACV immediately and completely cured all of my isle issues. It's been about 15,000 miles, and the issue has NEVER returned. The IACV cost was relatively inexpensive, but replacing it was a PITA - but absolutely worth it.

[max]

cel light stays off.
To fool the ecm into thinking the iacv is still connected i connected two 100 ohm resistors into the 4 pole connector as follows;



This solved the "cel" from blinking since the coils are around 100 ohms as well, i tried 470 ohms too but the ecu did not like these values so 100 ohms it is.
If you need some help locally just show someone technical this picture, they will know exactly what to do and put something protective around the exposed parts, we don't want to short out anything.
Also playing with the idea to put 100uf capacitors across each coil of the iacv, this may make the pulses last longer and giving the iacv enough time to move correctly, remember it's only just not running correctly and the two caps may just be enough to help it along, just guessing here with the scope readings in mind.

Just my guess but i think the permanent magnets inside the iacv are deteriorating due to heat, mechanically there is no reason the iacv is not functioning correctly and with the short pulse with it is just not enough energy to motivate the piston reliably, see Dave's results as well.

Thanks for your input Dave!

[PowerDubs_imp]

Yeah a little kick in the butt from a cap sounds like a good experiment.


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