Fast idle, stepper motor?

[oldtownduc]

My '10 Monster 1100S with Termi slipon and performance ECU just this morning started behaving badly.  Idle, which was typically at 1200 rpm, now seems to be at 3000 rpm.  Also, if idle ever does go back to "normal" 1200 rpm, and I touch and release the throttle (say expected 300-400rpm increase) the tach will jump to 3000 RPM and stay there for 4-5 seconds before returning to normal 1.2K RPM idle.

Throttle/cable is fine, it immediately returns to base position and does not stick.  When starting the bike it will immediately jump to 3000 rpm with no throttle input.

My research points to the stepper motor sticking in the open position.  Is there a way to easily test this by disconnecting it?  I've located it but need a way to disable/test it: can I disconnect a harness or simply pull a fuse?  No garage available so I can only do simple troubleshooting before bringing it to the dealer.

Thanks for any help.

[Bill in OKC]

I have an S4Rs and if they work the same, you can disconnect a 4 position connector from the stepper.  There are two rubber hoses that connect the idle valve to each throttle body - also make sure they are connected and/or in good shape.  If the valve is stuck it is a bit of a pita to get it off but you could inspect it and maybe free it up and try spraying a little wd40 on the mechanicals.

Since the idle seems to stay high when the throttle is opened you might be looking for a vacuum leak somewhere else.

[oldtownduc]

Thanks, searching vacuum leaks brings a whole boatload of valid results which I will have to check.  My initial inspections could find nothing out of place, but this wouldn't be the first time something has come loose on this bike.  The charcoal canister is removed (by someone else), I will double check that.

[danaid]

Thanks, searching vacuum leaks brings a whole boatload of valid results which I will have to check.  My initial inspections could find nothing out of place, but this wouldn't be the first time something has come loose on this bike.  The charcoal canister is removed (by someone else), I will double check that.

 There are some who simply plug the vacuum nipples, when removing the charcoal canister hoses, with rubber vacuum caps. These caps  eventually dry up, crack and loosen or fall off.

 This is something you should check. Un bolt the vacuum nipple from the manifold and use a bolt as a plug instead ( can't remember the size, m6 ? Hopefully someone else will chime in.)

Good luck!

[oldtownduc]

Did a little more investigation this morning.

Looks like the charcoal canister was removed properly - they removed the nipple and used screws in the manifold. The screws were snug but I removed and retightened them anyway.

I started it up - lately it has been taking two tries to start which is not characteristic of this bike.  First time turning ignition on, bike will not start no matter how many/long I press/hold the start button - after turning the ignition off and back on it starts right up.  I'm not sure if that is related to this problem or not.

When it started, RPMS went to 3000, stepped down to 2000 in about half a second, and then down to normal 1200 in another half a second.  I let it idle normally for about 3 minutes.  I barely touched the throttle and it jumped to 3000 rpm, stayed there for about 3-4 seconds and then went back to 1200.  I repeated the process numerous times with same results.  This is slightly different than yesterday, where the bike would just seem to "stick" at 3000 rpm.

I took a picture of what I think is the electrical connection for the stepper motor.  By unplugging this, I assume the stepper will remain in a "closed" state and not interfere with anything?  Does anyone know if there are schematics/photos of stepper motors floating around?

Picture of right front side of the bike, with air-flow plastics removed:

[Bill in OKC]

That looks like the connector.  My connector is right on the end of the stepper body.  When I unplugged mine the pins were starting to turn green...  Water had somehow found its way in there.  IIRC I used a cotton swab with some oil to clean the pins.  Maybe you have a bad electrical connection?  

[Howie]

Yes, the idle should drop below 1200 when you disconnect the connector.  Might even stall.  The throttle should also hit the stop screw.

[oldtownduc]

Thanks all, I'm open to any and all ideas at this point.

[oldtownduc]

OK some new info - I unplugged the stepper motor electrics, the plug I took a picture of previously.  Motorcycle immediately started right up on the first crank.  Check engine light illuminated (expected).  Idle would jump back and forth between 1200 rpm for 2 seconds and 2000 rpm for 2 seconds.  More importantly, when I would blip, touch, or do anything with the throttle, the idle would immediately go back to 1200 or 2000 rpm, and never "hang".

I plugged back in the stepper motor and fired it up again - now it consistently idles/hangs at 4000 rpm.  That's one mean-sounding idle.  Check engine light went off.

I think this pretty much narrows it down to either the stepper motor is jacked, or, something is telling the stepper motor to do bad things.  Sound logic?  Next step I suppose is trying to unplug the stepper hoses and lube up the stepper internals.

[danaid]

 Regulator/rectifie?  Before mine went out on my 696 it started to do some funky things like not fire up on the first try.

[bebo]

I have a 2010 1100s and today have the same problem. Prior to today i had "sticky" throtle from closed position: no problem once the throtle has rolled on but if i returned it to closed position fast, for example quick blip then let go of the throtle, it would stay stuck there, i would have to use reasonable amout of force to open the throtle again.

So i took the bike to my local mechanics. Before i proceed, i am in Hanoi, Vietnam and we have only had Ducati showroom for the last few months and their mechanics is next to useless. I, like most riders in town, take my bike to "local", experienced but no formal training from Ducati, mechanics.

Anyway, the mechanics said the problem was due to dirty caburator meaning the throtle butterfly/fly, execuse me if the term is not correct, would stay stuck because of the dirt built up overtime. So the cab was taken off and cleaned. The sticky throle issue was no more. But that was when the bike has the issue you described. If i bring the rev up, it will return to 2.5k, stays there for about 2-3 seconds then returns to the normal idle of 1.2k.

I have tried reset the TPS with no success. My mechanics says it maybe to do with the ECU (i have Termi slipons with DP ECU too) not being used to slightly new/different fly closed angle and thinks that the issue will go away with time as the ECU adaps to the cleaner cab and closed angle of the fly.

I will try fitting the stock ECU to see if what the mechanics said is right as the stock ECU was removed when the bike was virtually new with clean cab.

[Bill in OKC]

I have heard of a ~?similar?~ problem on a ahemharley forum.  It had to do with the throttle position when the bike was turned off.  The ecu 'assumed' the throttle was at the closed position when the key was turned off and used this to calibrate something internally.  If the throttle was held open a bit when the key was switched off the idle would be high the next time the bike was started.  Harley fixed it with a software update.  I don't know if the new Ducatis might be doing something similar but try turning the key on and off without starting the bike and then starting it.  Quick and worth a try I guess.

[oldtownduc]

Thanks all for the ideas.  I've been reading lots about this problem on different forums.  My best guess is that either the stepper motor (idle air control) is just straight-up jacked, the TPS (throttle position sensor) is bad/dirty, or there is a vacuum leak.  Unfortunately without guidance or technical diagnostic tools (such as VDST http://www.desmotimes.com/product911.htm) I think I'm just at a standstill at the moment.  My appointment at the shop is next Tuesday and I'll update the thread with what they find.

[oldtownduc]

The shop seemed to quickly fix the problem by "resetting the computer to 0".  They suspect the throttle wasn't returning to 0 and when the computer tried to compensate everything just got all out of whack.  Mechanically the throttle was certainly returning to "0" - so perhaps they zeroed the TPS sensor.

If it happens again, it's a VDST for me.  I hate not being able to fix my bike for something so simple.