So it's my turn to experience a throttle actuator failure. My M5 is a March 2006 build SMG car with 94,xxx miles, based on the date stamps on the actuators themselves, these are the original units that came from the factory. Seeing as how these are obscenely expensive for what they are (read: poorly designed POS's), I thought now would be a good opportunity to try some of the fixes outlined by fellow board members. Unfortunately, so far I haven't found a fix and I'm looking for some feedback.
My failing actuator only caused my car to go into Limp mode after a restart, once the engine was warm. If I cleared the codes and waited for the engine to cool down, the car started and drove fine.
Post Intake Manifold Removal:
I examined the throttle linkages and opened and closed the valves by hand, I found that my car had the typical squeak other members had reported. Both banks had significant resistance when opening by hand. Part way through their travel you could feel them hang up due to dirt/lack of grease. I took the time to lubricate all of the throttle bodies to help relieve some of the stress on the actuator motors and gear assemblies. They actuate much smoother now, no more hang ups while moving. Moving forward I'd opt to re-lubricate these anytime the intake manifolds are removed.
by Jonathan Santarsiero
, on Flickr
Pre Tear Down:
Examining the gears:
I expected there to be significant wear considering these are original to the car. What I found was next to no wear on the white center gear, and the typical tooth thinning on the half moon spring loaded gear. I forgot to snap a pic of the reduction gear, but there was very little wear to be seen.
Lots of dust I assume from the gear wear...
I found some slight discoloration on one of the MOSFETs on the failing actuator. So I opted to try and swap that out seeing as how a few members on M3post had reported success doing so. Unfortunately, this did absolutely nothing. The slight discoloration seen appears to be from the coating applied to the board at the factory, not from a failed component.
Next, I'm considering having the DC motor rebuilt, but my gut says this is another failed component on the board. Any idea what component(s) would work fine when cold and then fail when hot? I still haven't replaced the gears but I'm not convinced new gears would remedy it at this point.