CB1100 Idle speed instability problem

[Lord Popgun]

Riko, tell us how you really feel

I almost bought one of those things before the CB came out. Dodged a bullet huh?

[Riko_imp]

how I really think?

better no bike than a Deauville?

All silliness aside, its a proven bike, bullet proof and a real charm when dealing with shi**y weather conditions like I have encountered (my loan bike has the full deflector kit at the sides and at the feet).

My loaner has even 80.000km and still felt very confident.

[dave]

I am very anxious to hear what the dealer finds on Riko's bike. The same situation on my bike is getting worse. Started the ride yesterday with a 1500 RPM idle (after warm-up). We rode a few miles in town, stopping at about 8 or 10 stoplights before stopping for a bite to eat. Each time the idle speed was 1500 RPM. The bike sat for approximately 1/2 hr before restarting and when I did restart it, it idled at a perfect 1100 RPM. This lasted for about 30 minutes, and a dozen or so stops, before it started the "low" (600) RPM idle thing again at every stop. The motor stalled three times, but more often when coming to a stop, in neutral, the RPM would drop to 600, then slowly work its way back up to 1100. Parked the bike for about two hours when we had dinner, and when I restarted it it was back up to a 1500 RPM idle again. By the time I reached home it was back to the 600 RPM idle mode. Based on another post there's a good chance this is the Idle Air Control Valve (IACV), but since I don't have the diagnostic capability I don't want to replace it unless I am convinced this is the culprit.

[ericlo69_imp]

Hi Dave,
As we know that HONDA is trying to find the root cause and solution so far, and some bikes’s problem are solved by throttle body assy. replacement “temporarily”. As the following attached post, this bike is out of warranty; this owner had no will to try the “unsure” & “high cost” solution. Therefore he sent his bike to parallel import trader (he bought bike from this trader) for throttle body clean, this was a compromise so far, he thought. Just cost him around 1~2 hundred USD. He has ridden ~1000km after that clean action, idle speed problem has no happened again; he will keep monitoring. For your reference.

One CB1100 (14'CB1100EX) owner suffers idle speed drop issue for several months; YESTERDAY he sent his bike to HONDA dealer, and dealer's technician diagnosed with computer, no any error code was found (as I mentioned before that problem will disappear temporarily if doing ignition off/on) ; Dealer said that so far no solution for this kind of problem, HONDA Japan is aware this issue, and trying find the root cause and solution.

It seems that the throttle valve assy. or idle speed motor were not the root causes!!!???

[Lord Popgun]

There is more to troubleshooting this problem than just hooking up the scanner and looking for fault codes. The TPS can be checked a couple of ways for proper operation. The IACV can also be checked and cleaned. Dave, in your case I bet just removing and cleaning the IACV and its terminals would solve your problem. If not, it eliminates one thing and doesn't cost anything except time if you do it yourself.

Hopefully some of these problems are not flakey ECUs. Honda isn't going to want to give those away.

[dave]

ericlo69 and popgun, thank you for your feedback. I am waiting to see what the dealer discovers with Riko's bike before I attempt any repairs myself. I'm really busy the next few weeks anyway, especially with the wife making me take her to Hawaii on the 11th and all. I hope that popgun is right, that it's just a loose or dirty electrical connection. The IACV motor isn't really that expensive, and I hope there is a test described in the Honda Shop manual that I can perform on it. Since I'll have the gas tank off I'll inspect the valves while I'm at it (just over 10,000 miles now).

[Riko_imp]

time for a small update, email from the dealer:

"There is a part on order for you but its expected here at the end of the month, meanwhile could you pick up your bike please, I will contact you asap when the part arrives.

In the Netherlands they have booked good results so far by replacing the IACV sensor, so we're going to replace this part first, but again, it's all experimental... "

Thus, next update early July, hopefully

[dave]

Thus, next update early July, hopefully

Thank you Riko. I am anxiously waiting for your reply. That's very interesting that Honda would ask you to pick your bike up, knowing that it was not running properly.

When you first turned your ignition key on did the buzzing noise, coming from beneath the gas tank, seem louder than normal? I used to think the buzzing noise was the fuel pump, but after reading my Honda shop manual I think this noise may be the IACV. The buzzing noise that occurs when I switch on my ignition key seems to be louder and to last longer than normal, and I don't know if this is a hint to the problem or not. Right now my bike is idling at 1,500 RPM. Who knows, the next time I ride it, it may go back to 500 RPM and stall again.

[Lord Popgun]

Dave, the fuel pump will make noise when the key is first turned on. If you put the kill switch in the kill position and turn on the ignition, the pump will not run but the meters will go through their check. I don't know if the IACV will cycle in that situation though. Gut feeling: It will, but I'd have to do some research.

[Riko_imp]

bike is in for installation of the FULL throttle body, according to the 2nd mechanic....and meanwhile they'll look into the failing gasket that causes the light oil leak at the gearbox side..