Bought a 52plate megane mark II nealry 4weeks ago, for 3weeks its been in the garage with a misfire. The car only misfires on tick over and sometimes struggles to start, will loose power every once in a while when driving but as soon as you switch it off and start it again this seems to go. The electrics seem to be faulty as the steering will only lock occasionally as well and have a service light that comes on and off and just recently started givong a message of check injectors with an engine management light. The garage cant seem to find any fault though from what i can see they haven't actually replaced anything, apart from what i've paid for myself.

Has the car been code read?

Saw a similar issue on another Megane recently - turned out to be the variable timing controller on the inlet cam.

It could however be one of a few things and will need to be code read before you start changing parts as it could be one of so many things.....

It has but it just comes up with a list of possible things that could be wrong, p0303 was the 1st code it came up with which was a misfire on number 3cylinder then it said multiple misfires now check injectors. The ignition coils have all been replaced along with the spark plugs but this changed nothing.

Very similar fault codes that I got with valve timing wrong (on a completely different car) so Stuy may be spot on.

Does it rattle on start-up?

Hi, I had a similar problem with my Renault Clio, coming up with all sorts of codes. One code that kept coming up time and time again was the MAP sensor. which was changed 3 times until myself and Diggin Deeper (who I will be eternally grateful too) took the throttle body off and cleaned the idle sensor. And hey presto the car has been running trouble free for months now!!
There seems to be a problem with the sensors on the renaults, that are totally misleading. The code could tell you it's one particular sensor, when it's actually not that sensor at all. As with my case!! All I'd suggest is go through all the sensors one by one, unplugging and plugging in again, could just be a loose connection.

http://www.renaultforums.co.uk/

This was a really big help to me, when I was having problems. There are a lot of "renault" knowledgable people on there.

i have a the same problem with management light being on full time took it the garage and they said nothing came come up the check so much to say its being driven around for the past two years with no problems what so ever and passed two mot's

Take throttle housing of, give it a good spray with carb cleaner, including in all holes in it, and check your ht leads., also if you have replaced parts on it, disconnect battery for 2 hours so clears ecu, and so it can relearn that faulty parts are no longer faulty. And it will relearn your driving style again.

it wont pass new mot test coming in in Jan, if engine E.M.L is on it will fail mot same as airbag light.