Engine stability problem

[titi83550]

hello everyone

I have a 2011 R1200RT, it hasn't been running for 1 year and now when I start it the engine is unstable.

Here are the symptoms, the idle is stable but when I touch the gas pedal even a little bit, the engine accelerates quite strongly (3 or 4000 rpm) then slowly goes down to idle.

I plugged in an OBD2, then with BMW MOTORSCAN I could see that there was a fault on the exhaust valve.
I dismantled it and it's stuck in the fully open position, which shouldn't cause any operating problems.

I then balanced the cylinders, locking the idle motors, and in this case I was able to eliminate the engine acceleration problem. However, as soon as I put the idle motors back on, the problem started again (unstable engine acceleration as soon as I touched the throttle).

I've also checked the throttle position sensor, which works normally.

Additional information:
if I disable the idle stepper motors with motorscan, and then disconnect them, everything works normally.
however, as soon as I connect one or other of the idle stepper motors, the problem appears.

Do you have any idea what the problem is?
Thank you

[David.]

Could the problem be the stepper motors themselves, viewtopic.php?t=4668

[Nick Evans]

Once upon a time I had something like this happen to me; turns out the cable from the cruise control module to the throttle was not correctly routed and this caused the engine to rev uncontrollably.

[titi83550]

hello everyone,

I performed the following tests:
- TPS sensor: OK
- 2 x idle stepper motors OK
- Cleaning of the entire intake assembly OK
- Temperature and air pressure sensors give correct information with MotorScan
- Cylinder synchronization OK

Symptoms:
- At start-up: the engine rises to 2000 rpm then falls back gently to 1000 rpm.
- If I accelerate just a little, the engine instantly climbs to 3000 rpm, then when I let go of the gas pedal it drops back to 1000 rpm very slowly
- If, once at idle, I disconnect the 2 idle stepper motors, everything works normally again, acceleration is again perfectly controllable and regular, and when I let go of the gas pedal it immediately drops back to idle speed.
- if I reconnect the 2 stepper motors (or even just 1), the problem starts all over again.

Isn't there another sensor that manages the position of the idle stepper motors ?

Thanks for your ideas.

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