6 months ago had cam sensor replaced folloiwng EML coming on. Had no problems for 6 months and then had trouble starting the car and cutting out whilst driving. When cut out did start again pretty much straight away however driving has been very jerky and feels like no power in getting up to speed. The car has since failed to start at all now however we removed the crank shaft sensor, started ignition and car started straight away. Turned ignition of, replaced the sensor can car started again perfectly and drove perfectly with no juddering etc. Started car an hour later and againstill fine however come next morning back to not starting. Did the same thing again with the sensors and again started fine but next day failed to start. Anyone have any ideas. Have been told its the timing chain but would the car still drive perfectly (when first started) if this was the problem.

Any advice much appreciated. Thanks in advance