C270 CDI revving high in a gear

[vieroli]

I have a C270 CDI that I bought new in 2002. Initially in its first year, but only occasionally the car would lock in a gear when you step on the gas and it shifts down. You would then have to stop and turn off the ignition, then start again and it would be okay until it happens again a few weeks later.

The computer at the agents did not show up the fault and it was not fixed. This year the agents said it was the air mass sensor which was replace twice, but now the car revs high in each gear before it changes to the next. It would also shift down, when not necessary. This happens every day, although it may not happen when the car is cold, but after some time it would start again.

The agents say it is a mechanical fault in the gearbox as it is not showing on the computer.

Is there anyone who can give me advice in this problem?

 

[Glenn Smith]

Sometimes when a new component is fitted it takes some time before the gearbox adapts itself (ie learns the new characteristics of the engine, with the new compnent fitted) i doubt it is a mechanical fault in the box as the changes are occuring and the shift points are controlled electronicly. how high does it rev? with how much throttle? do the unneccessary down changes occur when accelerating from a steady speed or just randomly?

 

[vieroli]

steady speed

All happens at steady speed, it is not done at full throttle as we are afraid that it may get stuck in a gear again. It revs to 4000 before changing. The down changes happen at steady speed.

 

[recycled]

i think the ATF might need looking at as well. how many miles have you done on this. they tend to hold gears to get lubrication going on

 

[vieroli]

The car has done 183 000 km but the latest prblem has been going on for the past 4 000 km

 

[recycled]

when was the ATF/ gearbox filter last changed

 

[vieroli]

I will have to check. I can't say off hand

 

[panason1c]

This year the agents said it was the air mass sensor which was replace twice

It does sound like a maf fault...did the garage fit a genuine MB maf?

Try disconnecting the maf, (unplug it) and then drive the car....it should run through the gears ok (except for no kickdown), if it does drive relatively normally then i would suspect the maf.