I've recently purchased a Renault Megane convertible for my wife and in one week it's been at the mechanics more often then not! Had 2 out of the 4 spark plug sensors replaced and also have a problem with starting the car in the mornings.

When starting it up it doesn't tick over,it just cuts out. I've noticed after revving the car for 5 mins the revs settle down on about 400rpm. My mechanic put a diagnostic test on and nothing came up.

Looking through forums it could be a number of thing(camshaft sensor,new battery needed).
I've never owned a Renault and regretting it already!