I have just purchased a 2nd hand 1.6 16v ( about 2 months ago ) and I have had this problem since purchase, the car has been in the garage 5 times in the past 7 weeks and they still cant find the issue.
I have managed to get my hands on some of the Renault technical notes
and have found out that new dephaser pullys that are sent out as spare parts are not locked, there is an inner hub on the dephaser pully that needs to be turned until it is locked in place before the part is fitted to the new engine, what they found is that most of these were not locked when they came from Renault Spares and this causes the timing to be affected and the car will lose power and hesitate especially when the unit was cold, once the engine had warmed up this issue would dissapear..... this is exactly the fault that we are all having
Now I have gone through more of these Actis Solution updates (Renaults technical support database) and have found that the following needs to be tested for the above fault K4M 760 - 782 Engine models:
1: Check if injection software is older than A7.73 if it is then update with V31 or newer ( They use Technical Note 3585A for doing this update )
2: Test the camshaft dephaser solenoid valve - Replace if need be
3: Test camshaft dephaser pulley - Replace if need be ( This needs to locked before it is fitted )
The above is from the 4432A technical report for instability and engine hesitation
What it seems is that they are not locking these in place before fitting... hence some dephaser changes are fixing the problem others are not.
Mine was replaced 2 weeks ago and it did not fix the problem so i am sending the car back tomorrow to be checked out again, will ask for a full report on what has been done and will be telling them about locking the dephaser pulley and also about technical note 4432A and to try that.
I know that the dephaser pully, tensioners, timing belt and 2 sensors (dont know which ones but will check) have been changed so far.
I have a full 2 year extended warranty when I got the car so if it takes Renault 2 years and thousands of pound of there own money to find out what the issue is then they will have to do it... rest assured I will find a resolution for this problem....
Will be in touch shortly