Hello,

Last August I purchased a used 2005 C320 4matic. I've since put 2k miles on it, bringing the car's total mileage to just above 60k.

The car was running great, although I felt the automatic transmission was a bit hesitant. After a bit of searching around I found a procedure for resetting the throttle (with all windows up, turn ignition to the second position, hold down the gas pedal for ~ 10 seconds, then turn the car off while continuing to hold pedal, wait 2 minutes before starting the car). Forgive me if the details are off, as this was several weeks ago. The process seemed to work and the car was shifting much more spryly after driving it around that day.

However, the very next day the car started having trouble starting. In the morning the starter would turn over and over again without starting when using the one-turn start (prior to the reset it always fired right up). After trying it again it started up so I drove to work. The idle was rougher than before. That same day, upon trying to leave work, same issue starting. Then the engine died at a red light on the way home.

I got it over to my mechanic who was actually unable to get the car to start at all and thus did what he described as a full reset to the various adaptations at which point he was able to get it to start. He scanned for faults and found none.

That was about two weeks ago, since then the car still seems to drive a bit rough to me and I noticed that I'm averaging ~ 2-3 mpg less than I did before this whole ordeal. Then today, when I went to fire the car up to go to work, same issue with starting and again on the way home from work.

Any ideas what may be causing this issue and why the throttle reset procedure would seem to induce these issues? I poked around the forum for this problem, and while I found some similar issues mine seemed to be different enough to warrant a thread. Any and all help is greatly appreciated.