A friend recently bought an 1998 E55 AMG. When he got the car, the AFM was disconnected, and the car ran relatively ok, except sometimes stalling.

Replaced the LMM with a new (known brand, not no-name junk), and the fault codes disappeared - but the car acts up. When just letting it idle and creep, it will be just fine, but as soon as you touch the gas, the car starts bucking and "jumping", but it does not miss. As soon as it somehow stabilizes, it runs okay, and power is just as it should be.

No fault codes (with Star), thinking I should read the air flow values, but can't find any specifications on what it should be.

Any ideas on what causes this problem and what to check?

__________________
'95 E36T AMG (124.092)
'98 E200T (210.235)
'00 E430 4Matic (210.283)

I would look at the o2 sensor. How long has the amm been unplugged?

__________________
1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

I don't know for how long, but probably quite a while. The previous owner did some stupid hacks (cut off the exhaust, pulled the ESP fuse etc.), so I doubt he ever looked at it.

I can check the O2 sensor live data with Star and see, plus try unplugging it and see if it makes any difference.

__________________
'95 E36T AMG (124.092)
'98 E200T (210.235)
'00 E430 4Matic (210.283)