My apologies for the vague description (im posting this for my partner's friend), but thought someone might recognise this sympton...
Car : 146 1999 1.8TS red
During acceleration (30 - 40mph I believe) the car stutters. It seemingly acts as if you have jumped off the gas and then back on. From then on its fine. I asked if she thought it happened at a particular rev or gear, but she wasn't sure. She is pretty positive that it isnt anything to do with the car being cold as it can happen at anytime.
The car has already been into the garage (and had "something to do with oxygen" replaced) but the problem is still occurring.
"(and had "something to do with oxygen" replaced)".......guess this'll be the Oxygen sensor (lambda sensor).
Lambda problems (misfiring/hesitation/cutting out/high revving) usually come at any speed/revs so back to the garage methinks! Idle actuator possibly but this usually causes problems at lower speeds/tickover.
Might be worth checking all the plug leads and well. Oil can leaks into there from the rocker cover gasket and allow arcing to occur. Have the plugs been changed yet?