Sclass auto gearbox jumpy why?

[s500surrey]

My 99 S500's (99-05) auto gearbox is playing up. When accel at full tilt, the engine just revs on a low gear and refuses to "click" into the right gear. Also, random jerky changes... A real shame - gone from 0-60 in under 7 secs to being outraced by a 316i.. What gives?

 

[Seamster15]

Could be the Maf sensor.
Try reseting the gearbox.

Turn the ingnition on (dont start the engine), Push the excellerator to the floor for 5 seconds, turn off the igntion, release the excellerator.

I'm sure this is the correct proceedurem, I will double check later.

 

[s500surrey]

I'll give it a go... Thanks

 

[KLP 92]

Could be a gearbox failure as its quite common on a W220. A slightly better description of the fault may help.

 

[Dieselman]

Could well be hte MAF sensor giving dodgy readings. This will cause the gearbox to hold gears and to bang into the next one.

 

[s500surrey]

Could be a gearbox failure as its quite common on a W220. A slightly better description of the fault may help.

The fault is 2 fold
1) Acceleration
Engine doesn't accelerate well from start but works well between 30-50mph (2/3rd gear in auto). However, at 4-5,000 revs it refuses to change gear and ends up revving close to the red line.
2) Gear changes
Gear changes come in late and are very clunky. The box is not as responsive as it was before the fault.

 

[stargazerplus]

Sounds like a mas airflow sensor fault... try unplugging it and see if there is any diffence... if there isn't then that's probably the culprit. You could also try cleaning it.. see the how to section, takes about 10 minutes. It can't hurt.
Sensor failure leads to limp home mode for the engine and may produce your symptoms.

 

[s500surrey]

Thanks Star... if I dont know where the airflow sensor is, would I be best advised not to touch it in the first place? Dont want to screw things up, but will have a go if its easy to locate.

 

[Shude]

Thanks Star... if I dont know where the airflow sensor is, would I be best advised not to touch it in the first place? Dont want to screw things up, but will have a go if its easy to locate.

It's a plastic pipe with an electrical plug going into the side of it. They're held in place by friction and a jubilee-type clip/clamp IIRC. You may have more than one of them...

 

[s500surrey]

OK interesting feedback from a dealer here currently servicing the car.

All those of you who identified it as the airflow sensor scored points, thats £500 thank you for the dealer for changing that...

Now there is a slightly more inoccuous issue regarding oil leakage
http://www.mbclub.co.uk/forums/showthread.php?t=28225

 

[s500surrey]

Oh and by the way - the gearbox reset according to the dealer "doesnt exist"... hmm... are we to believe them?

 

[Thmsshaun]

Is it still just the one sensor on the V8?