Another TPS Question

Symptoms. 2012 Roadster with TORS, Ramair, along with a Hanso map, unrestricted secondaries, with +5% extra fuel to prevent popping on decel. Been running this map for years.

Last year, on cold engine start ups, the bike fires up fine then hunts for about 30 seconds erratically until the idle settles down. It started doing this early last year. No other symptoms/problems though so I rode it all last summer. This year while in Florida in January, whenever I got to an intersection and had to wait for the light change, when giving it a bit of throttle, the bike would hesitate, stumble, sometimes stall and sometimes backfire. Once underway, there was no other problem. Drove it like that for a month. Decided to check it when I got home. Purchased a TPS.... just in case.

Back home now, I noticed something while checking the TPS. With TuneECU hooked up, I initiated "Adjust ISCV" and got .60 volts. Nothing to adjust here. I then double clicked for the second test and initially got .72 volts but after a few seconds it dropped to .66 then to .60 and then climbed back to .72 and stayed there. Did this a couple of times whenever I initiated the "Adjust ISCV" function.

Is this normal? Once it does the weird dance, it settles down and doesn't change at .72. I then clicked for the final 15 second part of the reset where it tells you not to touch anything.

Thinking this wasn't normal, I replaced the TPS with the new one I had and got the same weird dance on the .72 volt test whereby it initially goes to .72, then cycles down through .66, then to .60 and back up to .72.

I have checked all the historic TPS threads and haven't read of anyone getting this particular condition. Is this normal???

I'll test the bike again later to see if I still have the hunting condition on startup. Still can't drive here so I can't test for a stalling condition at intersections. I did have some gasoline in the old TPS which might have cause a problem with it????

Ok I'll add a couple thoughts. First back fires that could blow fuel out of the throttle body which might account for the fuel you found in the TPS. Again just thinking out loud. As for the throttle surge or hunting for the idle could be caused by the wet fuel in the TPS. But I've been looking at the throttle body and noticed a area that is spring loaded it will actually open and close the throttle plates. In this area is where I suspect idle happens without the throttle wheel moving which is how the stepper motor can adjust the throttle without moving the throttle wheel or cables. Again this is just some pondering on the idle problems. Anyway I've noticed a few other things while looking at it and wonder if there is enough debris in the mechanism to make it stick and not allow the throttle to return when the stepper motor retract to lower the throttle.
During this thought process I have found that adjusting the throttle plate stop screw to raise the idle mucks up the ISCV SETTING to such a point that its pulling on the stepper motor shaft trying to pull it out. In fact with the wrong amount of adjustment the nylock nut on the stepper motor will only be finger tight and eventually fall off. I'm still giving it more thought everyday. Anyway hopefully this is not confusing.

I had this when I put the hans0 map on my classic. I then used a different map with O2 enabled and it was fine. I'm guessing its to do with O2 vs non 02 sensor enabled and the inherent characteristics or your engine and air intake/exhaust. I've been riding on the O2 enabled map for months with no issues, I think we can leap to mechanical problems to easy, I think there is more too it, like possibly how your exhaust flows, etc...

I had the throttle control bug for years. Changed the TPS several times and the ISVC settings to no avail.

Try one drop of fine lubricant in the shaft of the pivot shaft where the actuator arm of the stepper motor pivots. That is to the right and bellow the arrow in Scotts great pic. Just behind the cotter pin. Dirt gets in there and interferes with the free play of the actuator arm causing the idle control problems. Some times it is the stepper motor itself which if faulty or dirty. Spraying lots of oil makes it worse since oil attracts more dirt. The actuator arm can be removed but then you have to adjust the master idle which is set at the factory. You loose the automatic shallow throttle control by the ECU/Stepper motor and have to throttle the bike to start it instead of just pushing the start button. That is the way most carburated bikes work any way; choke or throttle until the bike is hot. Good luck.

Temp this AM was 0 C. Typically the bike would start and hunt for 30 seconds or so increasing to around 1800 rpm then back down to idle before settling down. Since I changed the TPS yesterday and verified all settings .60 then .71/72, I took the time to lube the stepper linkage as @1K9 stated. Pulled the cotter pin and noted the linkage slid easily on the shaft. Lubed it anyway. The throttle linkage as a whole was pretty clean with little to no dirt on it. I then checked the ISCV again and verified the settings from yesterday. Started the bike and this time, no hunting. Let it run for 15 minutes. Had initial steady high idle around 1200 rpm then it slowly dropped to around 900. Checked the vacuum between the cylinders and they were spot on at 610. Can't take it for a ride yet but looks promising. We'll see if it stalls when I get it up to temps on the road in a week or so.

Still have the question regarding the second test for .72 volts. Should the voltage dance between .72 and .60 on the 2nd test for a few seconds before stopping at .72? I'm assuming it should now so long as it finally rests on .72 and is stable to allow adjustment of the stepper if needed??? Can anyone verify? Thx.

If its moving the idles should be moving. So ya you might see the voltage vary some.

As long as the voltage indicated stops wavering, you are okay. The ECU drives the stepper motor a specified number of steps when you click the button after setting the volts. Setting the throttle stop screw to read 0.72v calibrates the throttle to the ECU (matches the physical movement of the throttle blades to that anticipated by the ECU.)

Some people have changed the settings from 0.60v and 0.72v to 0.064v and 0.76v. The important number being a difference of 0.12v from the initial to the ECU driven states.

Gregger said:

Temp this AM was 0 C. Typically the bike would start and hunt for 30 seconds or so increasing to around 1800 rpm then back down to idle before settling down. Since I changed the TPS yesterday and verified all settings .60 then .71/72, I took the time to lube the stepper linkage as @1K9 stated. Pulled the cotter pin and noted the linkage slid easily on the shaft. Lubed it anyway. The throttle linkage as a whole was pretty clean with little to no dirt on it. I then checked the ISCV again and verified the settings from yesterday. Started the bike and this time, no hunting. Let it run for 15 minutes. Had initial steady high idle around 1200 rpm then it slowly dropped to around 900. Checked the vacuum between the cylinders and they were spot on at 610. Can't take it for a ride yet but looks promising. We'll see if it stalls when I get it up to temps on the road in a week or so.

Still have the question regarding the second test for .72 volts. Should the voltage dance between .72 and .60 on the 2nd test for a few seconds before stopping at .72? I'm assuming it should now so long as it finally rests on .72 and is stable to allow adjustment of the stepper if needed??? Can anyone verify? Thx.

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Sounds like a fix to me. Once I disconnected the control arm from the stepper motor and reconnected the stepper to the harness all was good. In addition Mufasa removed the idle butterflies from my throttle bodies and we changed the mechanic stop for the idle to about 900 rpm when hot. I have to throttle it to start and set the throttle lock a little while the bike warms up. I can live with that. Much better than the bike deciding to go to 2000 rpm in the middle of a curve. Good luck with your bike. They are all moody.

1K9 said:

They are all moody.

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That is why we refer to them as being female..

Grumpy Ole Codger said:

That is why we refer to them as being female..

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That makes sense.

However, being a rural kid growing up, I named mine Brahma. A big Bull who does what ever he wants when he wants and is only partially agreeable...