Quote:
Originally Posted by endofanera7
it's it normal to have both tva bank 1 and bank 2 go out at the same time?
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Absolutely. Or not far apart from each other.
Sal or others can confirm this part, but I believe the S65 DME commands the idle actuator fully open before opening the throttle actuators. So, for light throttle driving and idling, the throttle actuators are fully shut. I know this for fact on the MSS65 with the S85.
I have opened about 10 of these now which failed and every one was a result of worn teeth on the second reduction pinion gear and second reduction spur gear. The worn area (relatively small) coincides with the point at which the teeth are in contact when the throttle actuator is in its (installed in engine) spring return shut position. There is usually very little wear on other teeth outside of this range. I believe the wear occurs at idle due to the lack of rotary motion and and vibration of the engine nullifying the benefits of the PTFE injection in one of the gears.
Some people have reported they can realign the center (white) gear 180 degrees or so and the actuator continues to work for a while.
Maybe if someone (ahem Sal
) were to produce an improved gear set for the actuators made of a better choice of materials, we would have a long term, non $800 solution.
Anyway, since the failure occurs due to a mileage/run hours based cause, it follows that both would fail in similar time frames. I doubt BMW analyzed the choice of this Siemens actuator for or use in the S65/S85 based on a high MTBF rating.