2012 rt fast idle

[jjpen]

On ramp to interstate and ran the rpms to about 7000. The motor had been running perfect for about 100 miles. Now it ran rough and would not run less than about 4000 rpm. I got it home using the kill switch as necessary. I have checked the throttle and the butterflys in the throttle bodys are free and returning to their stops as normal. when I start the motor it runs about 4000 rpm with the throttle at rest. I removed the actuators and started the engine. Still idles at 4000 rpm. Any thoughts would be greatly appriciated. I could not find any info on testing the actuators.

[dirtrider]

10 hours ago, jjpen said:

On ramp to interstate and ran the rpms to about 7000. The motor had been running perfect for about 100 miles. Now it ran rough and would not run less than about 4000 rpm. I got it home using the kill switch as necessary. I have checked the throttle and the butterflys in the throttle bodys are free and returning to their stops as normal. when I start the motor it runs about 4000 rpm with the throttle at rest. I removed the actuators and started the engine. Still idles at 4000 rpm. Any thoughts would be greatly appriciated. I could not find any info on testing the actuators.

Morning jjpen

 

When you remove the idle actuators that opens the air by-pass ports & lets in  100% of the air they are capable of flowing. (that will probably give you a 4K idle rpm)

 

To get a low curb idle the actuators need to be in the throttle bodies with the pintles almost closed. (the more CLOSED the pintles are the lower the idle rpm)

 

Be VERY CAREFUL turning the key on, or running the engine, with the actuators removed from the throttle bodies as that can allow the pintles to screw all the way out & fall on the floor. They are extremely difficult to get reinstalled. 

 

I'm not sure that your original problem is/was related to the idle actuators but it sounds like you have an air leak into the throttle system between the throttle plate (or throttle plates) & intake valves. The idle actuators are included in this leakage path.

 

If both side throttles are FULLY returning to the closed stops then it doesn't sound like cracked (plastic) throttle cams but those do tend to fail during/after a wide open throttle event. 

 

Reinstall the idle actuators (caution: don't force them in if the pintles are extended) then turn the key on & off a couple of times (do not start engine) as that will re-set the idle actuators to know where home (seated)  is (if they are not stuck or failed). 

[jjpen]

Hey Dirtrider,  How do I test the actuators?  How can I make sure I don't let the pentels fall out and how do I get them back in if they do fall out?  Have you ever heard of a butterfly coming loose from the shaft?  That is what this acts like.

[dirtrider]

30 minutes ago, jjpen said:

Hey Dirtrider,  How do I test the actuators?  How can I make sure I don't let the pentels fall out and how do I get them back in if they do fall out?  Have you ever heard of a butterfly coming loose from the shaft?  That is what this acts like.

Morning jjpen

 

 How do I test the actuators? --- That can be a problem, the GS-911 will show the actuator command but not necessarily the actual pintle movement. If you try to run them when removed from the throttle body they can (quickly) screw all the way out then be pain to reinstall.  At work I have an electronic actuator (stepper) control box to manually work the actuators looking for engine RPM change. 

I also have a few cutaway (sectioned) throttle bodies that a stepper can be installed into so the actual pintle movement can be observed (usually trying to observe & catch an actuator that the pintle position gets lost)   

 

At home (IF) you know how the actuators work & how the control function works then you can play with the key-on or key-off unplugging the stepper at just the right time in it's reset stroke to allow it to remain in a certain position. 

 

How can I make sure I don't let the pintle fall out-- Easy, just don't ever turn the key-on with an actuator or actuators removed from a throttle body

 

And how do I get them back in if they do fall out?-- Depends, sometimes you can turn & wiggle the pintle within it's thread play to try to get the pintle threads to re-engage. If you can get it started into it's threads & get it in far enough that the pintle won't rotate then you can start it back into the throttle body & get the screws in a couple of threads to hold the actuator at that position (screws just snug). Then while pushing in on the actuator with a couple of fingers just turn the key-on. If done correctly that should allow you to push the actuator into the throttle body as the  actuator re-sets. (it might take a few tries to get the actuator to go all the way in, but don't force it). I have also had some luck by getting the pintle into the actuator as far as I can then pushing in on the pintle with my thumb as someone turns the key on & off (actuator needs to hooked to the motorcycle for this to work). Only do one side at a time.   

 

Have you ever heard of a butterfly coming loose from the shaft? -- Yes, I have even seen one of the screws sucked into the engine but  this usually occurs after someone has worked on the throttle body & had the screws removed for some reason.   I haven't ever seen an un-molested screw come loose on a BMW 1200 motorcycle. 

[jjpen]

I do not know the history of the bike but the pullys are in good shape.  Makes me wonder if they have been replaced?

[dirtrider]

1 hour ago, jjpen said:

I do not know the history of the bike but the pullys are in good shape.  Makes me wonder if they have been replaced?

Morning jjpen

 

It should be pretty easy to tell__ If the pully's (cams) are just pressed on the shafts with the end of the shaft lightly peened over then they are probably still factory.

 

If the pully's (cams) are fastened to the shafts with a screw & washer then the pully's (or pully's with new shafts) have been replaced.  

 

Replaced pulley (cam) on right in the picture below___

 

 

 

 

[jjpen]

I just pulled the throttle bodys and the pulleys are solid, the actuators seem to work the same, and the butterflys are firmly screwed to the shafts.  The shafts turn smooth and to the stops both open and closed.  I sure would appreciate some ideas.

[dirtrider]

1 hour ago, jjpen said:

I just pulled the throttle bodys and the pulleys are solid, the actuators seem to work the same, and the butterflys are firmly screwed to the shafts.  The shafts turn smooth and to the stops both open and closed.  I sure would appreciate some ideas.

Afternoon  jjpen

 

Any signs of the boots leaking between a TB & the cylinder head?

 

Any signs the TB base idle screws have been moved? (the screw position is marked with blue paint from the factory)

 

Otherwise remove your oil filler cap & sniff for signs of gasoline in the crankcase (possibly a dripping injector after shut down)

 

Is the vacuum cap on one side TB nipple & the purge hose still attached to the other TB nipple? Is the purge hose hooked up all the way to the evap canister?

 

Typically for a 1200 to idle that fast it has an intake air leak between the throttle plate & the intake valves. 

 

Maybe try unplugging each fuel injector one at a time with it running to see if you can define your problem more to one side or the other. 

 

 

 

 

[jjpen]

after inspecting everything I could think of I installed the throttle bodys and low and behold it runs fine.  Now unless it does it again I will never know what fixed it.  Thanks for all the help.

[dirtrider]

1 hour ago, jjpen said:

after inspecting everything I could think of I installed the throttle bodys and low and behold it runs fine.  Now unless it does it again I will never know what fixed it.  Thanks for all the help.

Morning jjpen

 

My first guess would be that you had an idle actuator stuck with the pintle retracted allowing too much air through the by-pass.  The idle actuators follow the throttle as you accelerate so that would sort of fit the circumstances for your failure.