CB1100 Idle speed instability problem

[GoldOxide_imp]

[Speed_imp]

My bike has been developing the low idle and stalling syndrome since it was almost new. At first it was hard to reproduce but with time and kilometers (60.000 Km) now it happens every time i get in traffic, it is annoying.

I can not read the DTC's but checked TP, IAT, O2, EOT sensors and IACV valve (each coil 105 Ohm). Everything looks right but while checking the signals to the IACV it confuses me 2 things

1- I get two differert types of signal. A) PWM like when switching ignition ON for 2 or 3 seconds, then it goes to zero, it also appears for less than one second at the moment of opening throttle or if you try to stall the engine (and these two last conditions are similar to heavy traffic driving, which is when issue takes place) B) Pulses randomly every now at then (I suppose the ones it controls the stepper motor with)

2- The signals are simetrical with the zero volt line as simetry axle. They switch between positive and negative.

I am gonna try to attach some photos

Anyone knows what type of signal is expected in each of the coils of the IACV valve?

Thanks!
So at last I think I can post the photos... This kinda PWM signal appears after switching ignition ON (for 3 seconds maybe), it also appears for less than one second at the exact moment of opening throttle from fully closed. As it is an old oscilo and because the speed (sec/cm) is quite low in the photo only appears a fragment of the whole signal, if you watched the video this signal goes from side to side of the oscilo screen because of a very simple optical effect.



this is only one of the coils, only one channel. It is strange that it switches between plus and minus. Both coil signals have same behaviour.

Then this is the other type of signal i found. It is like a short pulse but also plus and minus. They appear more often while trying to stabilize the idle speed, when stable they don't appear so often. Can someone tell me if this is ok?

[Lord Popgun]

Speed,

I am an electronics tech (as are a few others on the board) and have a scope. Mine is similar to yours, but is a Tektronix digital scope. If you can provide your exact test setup (like probe connections on the bike) I may be able to use my bike as a baseline.

Honda does not have waveform information in the service manual. WE have to find it out ourselves.
I have a diagnostic tool that reads parameters, but not waveforms. It gets its info from the ECM.
What year and model bike do you have?
Do you have a wiring diagram?

Without a diagnostic tool, there is a manual method of reading codes. Unless Peterbaron or LR or someone chimes in, I'll have to look up how. It isn't hard and you read the MIL (check engine light) flashes. IACV is code 29.

However, the first thing you should do is reseat/clean all connecters from the IACV back to the ECU.

There is a pretty in-depth guide for this problem posted somewhere here. A group of us did a LOT of behind the scene work on it and one member wrote the procedure. 105 ohms is within the normal range for both IACV readings (99-121@25c)

[max]

Helo Speed, thanks for posting your pictures, just went over the idle speed thread and found some links that may explain what happens.

Briefly; when the key is turned on the fuel pump pressurizes for two seconds and because the ecm has no idea where the iacv is set it performs a routine to make sure the iacv is at the end of it's range of 150 steps; the iacv opens completely with 65 steps, it then closes for 35 steps depending on the engine operating temperature, these numbers may not be correct but are in the ballpark.

If you start the engine quickly when the iacv is still stepping you may find the rpm's higher without touching the throttle before settling on 1050 rpm.
During normal operation the iacv adjusts every time the throttle is operated and also tries to maintain 1050rpm in idle ( tps position ), so it moves quite a bit.

it is not obvious from your description where your reference point ( shield of the probe ) is connected, if it is connected to battery negative that may explain why it can go negative at some point, if it was connected across a coil that may result in another waveform level.

( Hi Lord popgun Sir )

If you decide to do another test with both channels of the scope be careful to not connect both ground clips to the iacv wiring, ( however using both channels you can still use batt negative for a refence and show both traces at the same time ) that could produce a fault to the iacv driver transistors or equivalent and i assume you know the basics of stepper motors.

A similar test with led's in anti-parrallel across one of the coils is here;
https://www.youtube.com/watch?v=MFA5Mk4vS3c

And another explanation is here;
http://cb1100forum.com/forum/showthread.php?tid=12203

In short; we have not found an obvious fault with the iacv valve itself but it has always fixed the problem, i suspect wear or misalignment of the piston over time, interesting post though

( edit) it may be possible to get a software update on your bike ( europe ), i think Wisedrum has some info regarding that, it is not used in the us though.

[Lord Popgun]

Max, that suspected wear,binding, or misalignment is something I wondered about since we started investigating this problem. Glad to see someone else thought that too.

Didn’t one member have an open on his IACV?

[max]

Lord popgun i don't remember an open coil, that would set a code and would get the piston stuck somewhere in a bad place i think and cannot remember such a situation, what i have never been able to work out is how much the difference between the piston and the cyl housing actually is, maybe Dave has an idea, i never asked him back then.

[Speed_imp]

These are the settings of the scope



I checked both IACV coils buit in the image I was checking coil 1, Black/Yellow (A6) and Black Orange (a7) wires where I connected the oscilo. Both coils give similar readings.



I was not expecting values from 0V to 12V and -12V in the same coil. In the other hand, the only method for reading codes without the MCS is the blink code which will appear when setting ignition ON and side or central stand down? Am I wrong? MIL light has never appeared in the lifetime of the bike... and also have never seen any blinking code. Thanks everyone for any help given!

[Lord Popgun]

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.

[Cormanus]

Lord Popgun, Speed's bike is an EX from 2014-2016 sometime. See http://cb1100forum.com/forum/showthread....#pid129051

[peterbaron]

Speed, you are in very good hands (Lord Popgun & Max ) , therefore, there is no need to interfere from my side.

@ Lord Popgun, have no longer access to scope due to C-19

Speed, just out of curiosity:
* do you have any related electronic or mechanical mods on your bike?
* I can not read the DTC's , would like to know why?, as this should be one first step. This procedure is outlined in HSM on p. 5-13 -MSC INFORMATION, and I believe you have this book.

Here is some more info/threads about idling issue:

http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem
https://www.healtech-electronics.com/products/obd/
http://cb1100forum.com/forum/showthread....le+problem
http://cb1100forum.com/forum/showthread....le+problem