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Offline AvgBear

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Idle Stepper Motor Linkage?
« on: May 17, 2019, 10:39:13 PM »
After dying at-speed - several times - whilst riding and then re-starting after a brief wait and running normal for awhile, I've been trying to diagnose the cause.
The bike sat for a bit longer than expected but started as normal only to quit about 5 miles from home -- it did this several times. Each time I puzzled as to the cause and did "something" to try to rectify the problem. First I thought it may be a blocked gas tank vent and rode with the gas cap ajar -- still died after about the same distance. Then I accused the tank bag of blocking make-up air from entering the gas tank and put it in a pannier -- same problem at similar distance.
After a few more iterations of the same problem I decided to cancel my proposed ride and head for home. Of course, it stopped yet one more time. This time, though, I distinctly heard the stepper motor make its "fax" sound whilst sitting at the edge of the road pondering my fate.
I thought to myself: "That sounds perfectly normal." And, it probably was because the bike ran perfectly fine the whole 25 miles back home. In fact, I had a ride planned with friends the next day of over 200 miles and it ran fine all day -- and continues to run fine - as normal.
All I did when I got home was spray some ether (starting fluid) in the general vacinity of the stepper motor / idle linkage that night and do the same with WD-40 (cleaner / light lube) the next morning. I've concluded that my problem was dirty stepper motor & idle linkage -- something that's been mentioned on this forum many times; yet something I neglected to ever do.
There was never a MIL (check engine) set nor any other symptom of a problem. After the times when the bike died, if I tried to re-start, it would only fire occasionally and I knew it was in a no-run condition. Then - seeming miraculously - it would start as normal and run as normal -- for a while.
SO.., barring a more definitive diagnostic solution (which I'll gladly accept) -- I'm going with dirty stepper motor. And admonishing all to clean your stepper motor linkage (MK1s).
 
"I've a fine felt hat and a strong pair of brogues
and I've rosin in my pocket for my bow.
My fiddle strings are new and I've learned a tune or two
and I'm well prepared to ramble I must go."
Tommy Makem

Online chuckxc

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Re: Idle Stepper Motor Linkage?
« Reply #1 on: May 18, 2019, 09:20:09 AM »
If I understand this, you bike just stopped running while traveling. Even if the idle stepper motor was stuck, I can't see how that would cause your engine to cut out at speed because it has very little influence on the throttle beyond about 1500 RPM. And if it was sticking I would think you would have trouble starting, not engine cutout. It may have just been a coincidence that the problem stopped at the same time you took an interest in the stepper motor.
If you consider the usual culprits of an engine cutout, i.e. Spark, fuel, or air, these essentials make you suspect intermittent things like electrical connections, fuel pump, injectors, map tubing, coils, fuel filter.
Having a good look around the engine you might find someting not quite right.
A strange one.
« Last Edit: May 18, 2019, 09:21:59 AM by chuckxc »
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Offline healdem

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Re: Idle Stepper Motor Linkage?
« Reply #2 on: May 18, 2019, 10:02:22 AM »
I thought the stepper motor on the early models was only involved with setting and controlling the idle speed. it may be different for fly by wire models which will require something to convert the electrical throttle setting into controlling the fuel and or air inputs.


Online chuckxc

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Re: Idle Stepper Motor Linkage?
« Reply #3 on: May 18, 2019, 01:23:55 PM »
 It is  the 2012 model. That's why I wrote that I can't see how the stepper motor would cause an engine cutout at speed. Hard start problem maybe, but not an engine shutdown at speed.
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Offline AvgBear

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Re: Idle Stepper Motor Linkage?
« Reply #4 on: May 18, 2019, 03:46:37 PM »
Thanks for your replies.
Although the bike continues to run perfectly - as (almost) always - I still hope to get to the bottom of the issue with a proper diagnosis. From many years and miles (twenty-some thousand), I've taken its normal and excellent running for granted. Consequently, the concern over something that was so out-of-character and, seemingly, unsolvable.
My thinking centers on the Engine Management System: various sensors and the ECM (black box / computer) -- if it's not dirty/sticky idle stepper motor linkage. But, since no MIL / check engine light was enabled - I have my doubts in that area.
What if the computer compares stepper motor position - over time - and shuts-down operation when inputs don't agree for too long?

"I've a fine felt hat and a strong pair of brogues
and I've rosin in my pocket for my bow.
My fiddle strings are new and I've learned a tune or two
and I'm well prepared to ramble I must go."
Tommy Makem

Online chuckxc

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Re: Idle Stepper Motor Linkage?
« Reply #5 on: May 19, 2019, 12:21:48 AM »
I don't think the ECU would have that detailed a check, and even if it did, it wouldn't suddenly shut down while running. (The ECU doesn't  measure the stepper motor position directly,  it only measures throttle position, and the limit screw should prevent full closure.) The stepper motor may be a red herring. Given  it was a full shutdown of the engine, I suggest you start with the simple stuff first like a loose sparkplug cable or coil connector, the kill-engine circuit switches and connectors which involves the side stand switch, clutch switch, and kill switch, or dirty/watered fuel. It has to be something basic that would shut down everything at once. Not gradual. Even something as simple as a side stand movement and consequent switch action.
« Last Edit: May 19, 2019, 12:27:57 AM by chuckxc »
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Offline AvgBear

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Re: Idle Stepper Motor Linkage?
« Reply #6 on: May 19, 2019, 04:33:02 AM »
Thanks for your reply.
OK, I understand red herring... If it ever happens again I'll make sure to cycle those simple to get to switches. When it happens out-of-the-blue it's hard to focus properly whilst alongside a busy highway.
One thing: when the bike died those several times, when trying to re-start (and it wouldn't) it would crank oddly and attempt to fire what seemed like a cylinder or two -- a couple odd firings. Then, when it was ready to run (after some wait) it fired-up perfectly - as always - and ran normally.
I've experienced TPS issues on other bikes -- but think any sensor problem would cause MIL to light (no check engine light enabled) -- so, I assume no codes set?
Thanks again for the help.
"I've a fine felt hat and a strong pair of brogues
and I've rosin in my pocket for my bow.
My fiddle strings are new and I've learned a tune or two
and I'm well prepared to ramble I must go."
Tommy Makem

Online chuckxc

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Re: Idle Stepper Motor Linkage?
« Reply #7 on: May 19, 2019, 09:01:38 AM »
The first thing that comes to mind based on your latest description is fuel supply. Things to check would be in-tank fuel filter&fuel pump, injectors, injector connectors, a bad batch of fuel with water.
I say that because it eventually came good after some rough starting. Was there anything out of your normal routine regarding fuel?


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Offline AvgBear

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Re: Idle Stepper Motor Linkage?
« Reply #8 on: May 20, 2019, 05:11:57 PM »
*Originally Posted by chuckxc [+]
The first thing that comes to mind based on your latest description is fuel supply.
Was there anything out of your normal routine regarding fuel?
No, I buy fuel from neighborhood vendors like everyone else -- and they're not having a similar problem.
The one thing somewhat different was that the bike sat, in the garage, a bit longer than normal due to other circumstances -- but fired-up normally and ran perfectly (for a while).
Now, after several hundred miles, days of trouble-free operation, and a couple fuel fill-ups I'm still a bit 'ginger' to trust that everything's going to be okay.
I guess, barring a definitive diagnosis of the problem, I'll just have to go with "fuel"?
(altho, all my other vehicles display no problems w/same-sourced fuel..?)
"I've a fine felt hat and a strong pair of brogues
and I've rosin in my pocket for my bow.
My fiddle strings are new and I've learned a tune or two
and I'm well prepared to ramble I must go."
Tommy Makem

Online chuckxc

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Re: Idle Stepper Motor Linkage?
« Reply #9 on: May 20, 2019, 10:32:30 PM »
If it was fuel/water problem, I'd say it's ok now given the amount of trouble-free riding you've done since then.
Probably not necessary, but you might consider putting in one of the many fuel additives one time to mix and purge any residual water. Doesn't cost much.

(One possible scenario is condensation within the tank after a long sit. Any water settles to the bottom, but because the fuel intake is above the bottom, the initial start wouls be ok. Then, after moving out, it would slosh and get up to the pump intake level while on the road. Once in the fuel pipe/injectors, you problems began. And once through, all good again.)

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