My 2005 R53 with the automatic transmission left me stranded on the side of the highway, while trying to merge the car would no longer accelerate and began bucking as if it were trying to grab the next gear. This was dangerous as I had cars behind me and was trying to complete a merge when it unexpectedly refused to shift or accelerate, even when shifting with the steering wheel paddles the car wouldn't accelerate. I ended up pulling off onto the shoulder and attempted to accelerate again after coming to a stop, but still it couldn't even get above 20 miles per hour.

I shut the engine off, then tried again when it refused to start. It would crank and sounded like it was about to start, but the revs would die down and it stalled out. No codes came up during the failure to accelerate, I had to have it towed over 100 miles back to my mechanic.

Does this sound like a transmission failure or something related to the fuel system? Had been driving for over an hour and a half already at that point, but no indication that anything was wrong. Also had just filled up with a full tank.

 

The trans would usually give some warning before completely failing. Any issues with slipping or hard shifts in the recent past?
the lack of starting also points away from the trans.
Could be fuel pump or clogged fuel filter, really bad gas, like diesel instead of gas.
Crank damper failure?

 

Never had any trans issues in the past, only the occasional hard down shift (but this was fixed with new engine mounts).

I just filled it with 93 from Shell before I began the journey, it was fine for a while up until an hour in when it refused to accelerate. Crank damper is aftermarket, not the OEM rubber design.

I was thinking fuel filter, pump or maybe the ignition coils, I suppose I could have tried banging on the rear seat to shock it into working.

 

Turned out the problem was a bad fuel pump, replaced now and is working like new.

 

cool, glad you fixed it.