Recently we had a customer with an E60 M5 come to us with codes thrown for the electronic throttle on his car. Symptoms were the common car would start up from cold but once warm and shut off the car would not pass its own pre-start throttle check and go into limp mode. Rather than simply replacing the throttle actuators we wanted to open them up and confirm the real cause.
What we noticed was what others have noticed, some dramatic wear on the two plastic gears inside the actuator. The gears were almost completely worn out in the low throttle area just off idle where the throttles would be while cruising on the freeway. We also noticed that the gears that had the most wear also seemed to be actuating throttles that had more resistance. The driver side throttles on this car were particularly squeaky and dry so we cleaned all the linkages and lubricated them to help the new throttles live a longer life than the originals did. This car had 70k miles on it when it came in.
Since we happened to have an S65 on an engine stand we decided to open up that throttle actuator as well (although the part numbers are different) and see how similar the design was to the S85 actuator. We suspected that since the S65 actuators might have some different design inside that would be an improvement over the S85 but as you can tell from the photo there was no discernible difference. The housings and the gears actually had the same numbers cast and molded into them indicating that they were essentially the same part mechanically.
This particular early E60 M5 still had original programming and coding on it which might have contributed to some faster wear on the gears. We decided to program and code the entire car to give the owner the benefit of updated software on the DME as well as all other modules of the car. We typically find that the car seems to drive smoother after reprogramming. The most noticeable difference is usually in the SMG particularly at the more aggressive settings.
Once we were all done we noticed an immediate improvement in throttle response at lower throttle openings and the car seemed to respond much better to quick/large changes in throttle angle. This is a costly repair for something that might be easily repaired by replacing two seemingly inexpensive plastic gears. We are looking into manufacturing these gears locally to rebuild the throttle actuators on the S85 and S65.
Odometergears.com has informed us that they are working on tooling the gears for these actuators. That solution will not be available for several months. If you are experiencing problems with your actuators we encourage you to replace the set with new actuators from BMW so we’re offering them for sale at the lowest price we can afford to sell them until the gears become available: