Xsara Picasso 1.8, stutter

[2smv627]

Hi, my uncles complaining of a stutter when driving his 1.8 16v Picasso.
On tick over the thing runs sweet as anything and will rev no problem.
When you start driving it hesitates and and struggles to pull along although if you gentle on the throttle it will drive smooth. Car has no lights on and has been plugged in with no faults - any ideas?

Thanks