2.4 Jtdm misfire
Please keep us up to date with this - I have the exact same issues with my 159 2.4 Jtdm 200 and would love to know how / if you get this resolved.
Mine starts to run badly at 90 degrees, hunting at idle, occasional stalling. A bit of throttle to keep the revs even at about 1k helps at traffic lights. It's also a rubbish starter and needs a good bit of throttle to get it going first thing.
I've been told by garages that it's related to EGR. I've had several new ones and cleaned and refitted them myself. Not much difference to be honest. Then I was told could be the inlet manifold which is apparently expensive. I'm loathed to spend any significant money on it since it's been a money pit so far, and no one seems sure it will resolve the problem.