2001 A190 Erratic Revs W168

[Eastcotts]

Hi Guys,
I'm looking for some hope up here. We have a A190 W168 Automatic with the erratic revs.
It will start and then it doesn't react imminently to depressing an accelerator pedal, but once is over lets say 2000 revs it revs fine.
The computer shows Oxygen sensor problem, which was replaced.
Other things which we have done to it was:

• Full service
• New coil pack
• new spark plugs
• New lambda sensors
• New Crank shaft sensor
• Rebuild and tested airflow meter
• Catalytic converted was cut out to check if at fault and made no difference, so it was put back in.

Once you start driving it it goes ok, until you de-press accelerator or stop. On low revs it just sounds like throooon, throoon, throoon
When idle revs are going from 650 to 900 but not quickly its just at 650 for a while then it slowly creeps up and then it drops again. I have had 3 separate mechanics looking at it and every one had different opinion, from leaking air pipe to gearbox problem, but when gearbox disconnected it makes no difference.
Its an old car but in mint condition with only 80k done so I would love to save it.
Any idea?

Thanks,
Peter

 

[merc85]

Maybe the Airflow meter which is all part of the ecu on the pre 2004 models. If you have a look on youtube and your handy with a soldering iron you can sort in out without the extra cost of a new ecu.

 

[Eastcotts]

Done it already, see the list in original post.

 

[grober]

Have these cars got a drive by wire accelerator pedal/throttle? Your symptoms could be readily explained by a problem in either assembly -- the throttle pedal sender unit or the throttle actuator?

 

[area51]

Is the fuel filter ok? Non-genuine filters can cause problems.

It might also be worthwhile checking the fuel pressure to be sure that you haven't got a weak fuel pump.