how can i fix my renault Megane mk2 1.6 16v vvt?

i have a Renault Megane 2003 1.6 16v vvt hatchback. i have problem on idol The car starts after 5 sec it stalls till car is warm. engine management light came on and put it on computer it said camshaft sensor had tdc sensor changed and cleaned air intake still has problem.when i rev up to 2000-3000 rpm the revs start to drop & stalls start car again rev counter starts bouncing up & down again the car runs fine when warm. just on start up