CB1100 Idle speed instability problem

[Speed_imp]

The side stand method you posted is right. Also, no one with the problem reported any fault light or codes stored.

How exactly did you connect the probes to the wires? I know, sounds like I don’t have a clue, but if I check mine I want it to be like you did it.

I would appreciate if you could check that signal in a known good working one! I check the two coils of the valve separatedly as I only have one probe (so only one channel). I back probe the connector with two needles and connect there my probe, something like this (here the TP sensor, for the IACV same procedure but pins 1-4 or 3-2):



I checked the valve as per manual 5-41 and 5-42 and everything looks good, so I just wanted to see what the ECU tells the valve to do. On start up we have a PWM like signal for about 3 seconds (Ignition ON, engine not working yet)



Once we start the engine we have pulses I guess to control the valve position (I have not counted the number of pulses)



But then, with engine at normal temperature, out of the cold start phase, "sometimes" when opening throttle from fully closed this PWM signal appears again for less than a second. While I don't have the PWM on opening throttle from closed position the idle runs fine, when it starts appearing the idle starts going down (heavy traffic conditions, throttle from fully closed to opening and so on).



And this is what makes no sense to me, together with the fact that the signal goes from 12V to -12V. Of course I just can replace the IACV and then check if it works as designed again but I would hate to do all the job and... I think there is a member with same symptoms and IACV replacement did not help.

So Lord Popgun if I just could have a reference signal from your bike which is working ok I could rule out one component or another and go for a ECM (if you have different signal behaviour) or IACV (if you find same pattern) replacement with almost 100% success probability. (The theory always looks great )