05 Apr Lumpy idle on a clio 172/182 when cold
One of the most common reasons for a clio 172/182 to idle poorly is the cam timing is slightly out.
It is a speed vs density fueling algorithm on these cars not a mass air flow based one like on most modern cars so is a relatively unusual problem and fairly unique to have that in combination with also having fully floating cam pulleys on the same engine like on these cars so most mechanics wont have a clue about it.
So if you have something that makes a significant change to volumetric efficiency at idle like incorrect cam timing it means that the engine displaces a different amount of fuel per rotation of the engine than the data in the ECU has been programmed to expect.
As a consequence it delivers an incorrect fuel mixture and makes the car run lumpy.
When the car warms up the ECU then starts to reference the lambda sensor and switches over from the open loop fueling tables to the closed loop strategy and corrects itself in real time to compensate for the differences between VE and what it is programmed for on its open loop tables.
But people STILL insist on using shitty backstreet garages who dont understand the very specific requirements of these engines cause its a few quid cheaper than a specialist and then they wonder why they get problems!
Wear and tear can have a similar effect or can exaggerate the effect if its combined with slightly off cam timing.
If the problem is just down to wear and tear where the Ve drops as the rings get worn and dont seal as well and valve seal being imperfect compounds the problem then a remap (please not by some cheap and cheerful “chip tuner” with a slave unit who will make it worse as they wont understand the effect of adaptions on long term fuel trims etc, go to a proper renaultsprot specialist mapper) can often provide a suitable workaround for the problem, if all else fails then a slight increase in idle speed (like the RS Tuner remap introduces) is another way to solve it.
