2003 Renault Megane Car sometimes will not restart straight

STEVE_CARDIFF

MEMBER
2003 RENAULT MEGANE

Engine Mechanical problem
2003 Renault Megane Two Wheel Drive Manual 61000 miles

I own a Renult Megane Dynamique (52 plate), 1.6 engine. Car has been fine but recently I have had a few problems with restarting the engine. If I leave the car for a length of time and start it it operates fine, yet sometimes if I travel a distance, stop and try to restart within say, 10 mins then the engine will not start. I have to leave it for awhile and then start it. There are no warning lights at all and evrything else is fine. A couple of times the engine has cut out while waiting at traffic lights and again, struggle to restart.
My renault dealer couldnt find anything major except for a possible corrosion of certian wires. I got quoted £800 to replace the whole section and even then he couldnt guarantee it would definitely resolve the problem! From my own research I have come across a potential Crank Shaft sensor or UDC sessor issue. Is this right. Any advice (price to fix) greatly appreciated

can you help please?

2 Replies

MATHIASO

MECHANIC
1,209 POSTS

I believe the system on your vehicle (european new cars) regarding emission control is as follow:

-The UDC (urban driving cycle ) duration 993 second, cold start.
-RDC (road driving cycle) duration 1082 seconds, warm start
-MDC(motorway driving cycle) duration 1068 seconds, warm start

Those 3 sub cycles are part of the Common Artemis Driving Cycle
The CADC was created in Europe in order to gain a better knowledge about emisions in real trafic.
My point is, if the car do not start when warm up, the RDC or the MDC sensor might be at fault, because car do not start when warm.
I believe the UDC sensor is ok, because cold start is ok.
The crank sensor might be ok
price to fix it depend of your location in Europe, taxes, policies.