CB1100 Idle speed instability problem

[Bindir Dundat_imp]

Yeah it does that I play around with it while i'm stopped at the traffic light. It's completely normal on my bike. Maybe you guys never noticed it before. Also thanks for fixing my blunder earlier.

[the Ferret]

hmm I'm going to have to check mine out this afternoon

no prob on fixing the blunder.. it's kind of in my job description, plus it makes my paycheck worth while

[Bindir Dundat_imp]

I'll probably make a video when the weather gets warmer so you guys can see it.

[SportsterDoc]

Here is a link to another high idle video...hopefully better than the last one. Temperature in the morning was 42 degrees.

https://youtu.be/J5KvMBxo-sc

My 2012 CBF1000 also does that, it's very normal. I think it's called easy start for newbies.

Appears to be an ECM function with clutch switch.

The clutch switch has two wires (very easy to unplug):

Black connects to green/red, which goes to
ECM B33
Start relay
clutch diode

Black/white connects to green/white, which goes to
ECM B22
side stand switch

If you disconnect one of the two clutch switch wires, I would expect the idle increase to cease. If left unplugged, the bike would need to be in neutral to start.

This is not likely related to the low/high idle issues under discussion. This may to be an ECM program variant.

I have a 2009 CBF1000 and also 2012 CBF1000. The 2012 when you let the clutch out, RPM will increase 200 to 300 RPMs. That happens so it'll prevent it from stalling when engaging 1st gear. The 2009 CBF doesn't have that feature. I also read the last few pages on this and nobody mentioned cleaning their negative cable to the body. Sometimes corrosion gives you a lot of Gremlins. The one guy I remember that posted a few pages down changed his battery I wonder if he was able to clean the negative cable to the body so he didn't have any problems after that. The 2009 CBF is notorious for burning out stator. My preventive maintenance is to make sure that the ground cable is always clean and a battery gauge to monitor the stator output. So far, the 2009 is still running good. This thread really interests me because I have a used 2014 with 19000 Km that i'm looking at.

Amazing how many problems a corroded/poor ground can cause!
Although, other than starting, my biggest concern would be the three chassis/harness grounds:

Green/black for fuel pump and gauge
Green/white for ECM A22 & A23
Two green wires for forward lights, ground junction and ECM B4

There are three ring tongue connectors, but I do not yet know their physical location.

[Lord Popgun]

The ground point is under the tank, forward of the ECU by the upper cross brace (where the frame angles in to the head).

I’ll send you the manual page Doc. Give me a little while.

[Bindir Dundat_imp]

You would be surprised by what corrosion can do in a short amount of time. There's a few guys in Fireblade Forum who had to replace the stator a couple of times before they were able to trace the problem to bad grounding and fried wiring harnesses. It's always good to cover the basics.

[max]

Nice job mechanix, no doubt about the validity of the test, it proves the switch IS providing the input ( b22 sstand ) to the ecm, disconnecting it without even touching the lever causes the increased idle.

So why does it do that and is it a fault with the wiring?
+1 on sportsterdoc on the internal programming of the ecm, combined with bindir's findings i would agree that is the case, never noticed it before? could have easily missed it with all the enjoyment that riding such a nice cb1100 brings.
If it was a fault in the wiring it would persist when the bike is cold or warm, it does not do this and therefore unlikely to be a faulty ground, but still worth checking for corrosion etc.
If the negative battery cable has a bad connection it would quickly show up in a bad starting and dimming of the instrument cluster on application of the start switch at which point 150 amps flows through the cable and loosing 2 volts at this point could mean the difference between a good start and no start, this 2 volts would be 0.1 volt when the battery charges with 7 amps but would not have an effect because the sensor grounds come together on the frame at central points, engineers have discovered this ground pitfall and grouped the wiring accordingly ( check the wiring diagram ).

By the way i use my green neutral light as a battery tester, it dims as the bike starts, the more it dims the lower the battery capacity is, 2010 model.

So i would like to think of this as an undocumented feature honda has knitted into the later models to "assist" drivers in adverse conditions, ( but just never heard of this bahaviour and stand corrected/ like to hear from others as it could be a clue ) they just forgot to tell it to the printers of the manual.

Thinking about your explanation that this increased idle switch behaviour lasts for 4 miles longer than the original cold idle does make me think though, as far as i can work out the engine temp is sensed by the Engine Oil Temperature sensor below the throttle body, the other temp sensor is in the air intake after the air filter in the velocity stack chamber, but that should not change because it measures ambient temperature which does not change when the bike is driving.

From the video it appears that the iacv works fine and consistent in this part of it's travel range, it may be different in another part, though.
Briefly ; on startup the iacv is "reset" to the end of travel ( open, position 120 ) and then stepped to the cold position ( position 85 ) and gradually moves to it's operating position ( around 70 ) to maintain 1050 rpm, these are approx values to illustrate what happens, and conventional thinking is that the iacv has a problem around position 70 ( thanks popgun ) and produces the idle issue for reasons we are still trying to work out, it is quite hot in there during slow traffic and among other things may affect the magnetism in the permanent magnets in the rotor section of the iacv, weakening them, again ; speculation from me at this point

Have you noticed an increase in fuel consumption? that appears to be one of the symptoms associated with low idle syndrome.

Good video; max

[SportsterDoc]

The ground point is under the tank, forward of the ECU by the upper cross brace (where the frame angles in to the head).

I’ll send you the manual page Doc. Give me a little while.

Thanks, got it. FSM page 1-29

[johnf514_imp]

Just wanted to add my experience here. Same issue with idle rising when letting out the clutch in gear, but before any meaningful engagement. Also, the idle would typically rise just by putting the bike in gear, and holding the clutch in the same position (completely disengaged).

Nice job mechanix, no doubt about the validity of the test, it proves the switch IS providing the input ( b22 sstand ) to the ecm, disconnecting it without even touching the lever causes the increased idle.

So why does it do that and is it a fault with the wiring?
+1 on sportsterdoc on the internal programming of the ecm, combined with bindir's findings i would agree that is the case, never noticed it before? could have easily missed it with all the enjoyment that riding such a nice cb1100 brings.
If it was a fault in the wiring it would persist when the bike is cold or warm, it does not do this and therefore unlikely to be a faulty ground, but still worth checking for corrosion etc.
If the negative battery cable has a bad connection it would quickly show up in a bad starting and dimming of the instrument cluster on application of the start switch at which point 150 amps flows through the cable and loosing 2 volts at this point could mean the difference between a good start and no start, this 2 volts would be 0.1 volt when the battery charges with 7 amps but would not have an effect because the sensor grounds come together on the frame at central points, engineers have discovered this ground pitfall and grouped the wiring accordingly ( check the wiring diagram ).

By the way i use my green neutral light as a battery tester, it dims as the bike starts, the more it dims the lower the battery capacity is, 2010 model.

So i would like to think of this as an undocumented feature honda has knitted into the later models to "assist" drivers in adverse conditions, ( but just never heard of this bahaviour and stand corrected/ like to hear from others as it could be a clue ) they just forgot to tell it to the printers of the manual.

Thinking about your explanation that this increased idle switch behaviour lasts for 4 miles longer than the original cold idle does make me think though, as far as i can work out the engine temp is sensed by the Engine Oil Temperature sensor below the throttle body, the other temp sensor is in the air intake after the air filter in the velocity stack chamber, but that should not change because it measures ambient temperature which does not change when the bike is driving.

From the video it appears that the iacv works fine and consistent in this part of it's travel range, it may be different in another part, though.
Briefly ; on startup the iacv is "reset" to the end of travel ( open, position 120 ) and then stepped to the cold position ( position 85 ) and gradually moves to it's operating position ( around 70 ) to maintain 1050 rpm, these are approx values to illustrate what happens, and conventional thinking is that the iacv has a problem around position 70 ( thanks popgun ) and produces the idle issue for reasons we are still trying to work out, it is quite hot in there during slow traffic and among other things may affect the magnetism in the permanent magnets in the rotor section of the iacv, weakening them, again ; speculation from me at this point

Have you noticed an increase in fuel consumption? that appears to be one of the symptoms associated with low idle syndrome.

Good video; max

In my case, yes I noticed a material increase in fuel consumption. My bike doesn't seem to do well in terms of fuel usage anyway (<40 MPG around town), but I was getting LFL before 90 miles in some cases with the high idle. Also threw off a lot of heat.

[SportsterDoc]

The clutch switch is normally open (lever out for engagement), so as it is released the switch opens, which seems to trigger the higher idle. Jumper the two clutch switch terminals should prevent the idle increase, as reported.

My 2014 standard was warm from this mornings ride, so I did some tests:

With clutch switch disconnected, connected or jumpered, neutral or clutch pulled, idle is a tad over 1,000 RPM.

As clutch is engaged (clutch switch disconnected, connected or jumpered), RPM starts to drop. Without throttle, it will drop as low as 750 RPM as bike moved forward.

For Bindir Dundat, confirm this is the 2017, which may have a different ECM program, compared to 2010, 2013 and 2014 models?

Just wanted to add my experience here. Same issue with idle rising when letting out the clutch in gear, but before any meaningful engagement. Also, the idle would typically rise just by putting the bike in gear, and holding the clutch in the same position (completely disengaged).

Nice job mechanix, no doubt about the validity of the test, it proves the switch IS providing the input ( b22 sstand ) to the ecm, disconnecting it without even touching the lever causes the increased idle.

So why does it do that and is it a fault with the wiring?
+1 on sportsterdoc on the internal programming of the ecm, combined with bindir's findings i would agree that is the case, never noticed it before? could have easily missed it with all the enjoyment that riding such a nice cb1100 brings.
If it was a fault in the wiring it would persist when the bike is cold or warm, it does not do this and therefore unlikely to be a faulty ground, but still worth checking for corrosion etc.
If the negative battery cable has a bad connection it would quickly show up in a bad starting and dimming of the instrument cluster on application of the start switch at which point 150 amps flows through the cable and loosing 2 volts at this point could mean the difference between a good start and no start, this 2 volts would be 0.1 volt when the battery charges with 7 amps but would not have an effect because the sensor grounds come together on the frame at central points, engineers have discovered this ground pitfall and grouped the wiring accordingly ( check the wiring diagram ).

By the way i use my green neutral light as a battery tester, it dims as the bike starts, the more it dims the lower the battery capacity is, 2010 model.

So i would like to think of this as an undocumented feature honda has knitted into the later models to "assist" drivers in adverse conditions, ( but just never heard of this bahaviour and stand corrected/ like to hear from others as it could be a clue ) they just forgot to tell it to the printers of the manual.

Thinking about your explanation that this increased idle switch behaviour lasts for 4 miles longer than the original cold idle does make me think though, as far as i can work out the engine temp is sensed by the Engine Oil Temperature sensor below the throttle body, the other temp sensor is in the air intake after the air filter in the velocity stack chamber, but that should not change because it measures ambient temperature which does not change when the bike is driving.

From the video it appears that the iacv works fine and consistent in this part of it's travel range, it may be different in another part, though.
Briefly ; on startup the iacv is "reset" to the end of travel ( open, position 120 ) and then stepped to the cold position ( position 85 ) and gradually moves to it's operating position ( around 70 ) to maintain 1050 rpm, these are approx values to illustrate what happens, and conventional thinking is that the iacv has a problem around position 70 ( thanks popgun ) and produces the idle issue for reasons we are still trying to work out, it is quite hot in there during slow traffic and among other things may affect the magnetism in the permanent magnets in the rotor section of the iacv, weakening them, again ; speculation from me at this point

Have you noticed an increase in fuel consumption? that appears to be one of the symptoms associated with low idle syndrome.

Good video; max

In my case, yes I noticed a material increase in fuel consumption. My bike doesn't seem to do well in terms of fuel usage anyway (<40 MPG around town), but I was getting LFL before 90 miles in some cases with the high idle. Also threw off a lot of heat.

What model year?

Be helpful if the data to the left of the post (avatar, location, # posts, join date) also had model year or if everyone would include in the signature.