or_550i

Five times now, twice in one day, the transmission [or the combination of the engine and the transmission] sounds like it's gumbling when the gas pedal is pressed. The odd part is that pressing the gas down doesn't seem to do anything - the engine RPMs stay around 1300 (or at least it's greater than 1000 but less than 1500) and the car won't speed up until the gas pedal is either returned (no pressure) or pressed to the floor for a second.

The problem happens after costing or rolling along very slowly - like idling along a level street looking for a parking space or costing to a stop light. The issue happens after the car is already warmed up from a previous drive (no more than three hours earlier).

There are less than 19k miles on the car. It's a 2006.

Anyone have any ideas?

calpalmer

Mine ('08 550i with SAT) did this one time, in connection with a transmission "slam" as I was approaching a stop light, in DS mode, foot off the pedal coasting, and the transmission downshifted and slammed. Then no pedal response, rough idle... the odd thing was, I could put the trans into reverse, and back up just fine with pedal response. In forward gear, no response. I shut the motor down, waited about 10 seconds, started up, and all was fine, and has been fine ever since.

I reported this behavior to the dealer, but they couldn't see any codes nor reproduce it of course.

Cal

porsche911targa

DS will do that and that's all the dealers are going to say. The slam problem most everyone refers to is the one caused while driving in D.....

or_550i

Bah, It happened at lunch today.

I guess its a trip to the dealer.

calpalmer

You may be right.... but it's not acceptable behavior for any transmission, whether in Sport mode or not. In my case, I was on a two-lane narrowing to one-lane on-ramp to the freeway when it stumbled, and I was stuck in accelerating traffic creating quite an obstacle. When the light behind me changed, I experimented with backing up a little, but I was not going to be able to get out of that predicament safely by backing out, due to the blind curvature of the roadway. Luckily, the restart solved the problem, but ZF / BMW needs to get that taken care of as a matter of safety.

Cal

or_550i

And all the way home from work.
Oddly, using the steptronic mode worked fine. Maybe there's a controller issue. Anyway, have an appt. with the dealer tomorrow morning.

or_550i

RESOLVED!

The main service mechanic rode along with me today and about 60 seconds into our ride I began to explain the grumbling sound with the low RPMs and he said "I already know what it is and it's not the transmission." Then I was expecting some answer like Click and Clack that it was the driver who's the problem!

Turns out for those of us with the automatic transmission, on a long coast or idle through traffic the TCU/TCM tries to maximize the fuel efficiency. It does this by shifting to a high gear (4th gear in the e60) and then applies a lock-up torque converter. Read the wikipedia article - it sums up my experience.

The mechanic said that if I wanted to work around the problem, shift into manual or sport mode to prevent the TCU/TCM from trying to conserve fuel.

pigapumbu

Sounds like the quest for greater fuel economy is going to cause a lot of heartache in the years to come (as these cars get older). Thats my prediction what with all the electronics to manage fuel consumption, grill flaps, swirl flaps,... franky buying on lease and changing car every 3 years may be a better way to do it.

thanks for the post. At least there is closure and anyone with a similar problem can sort it out.

cheers