Car over fuelling/running rich

Hi all,

Took my car for an MOT and it failed the emissions test. Was told the CO2 level was at 10, exhaust smells of petrol, the car is running at 20mpg and I spend £20 in fuel doing a 60 mile round trip. Mechanic told me the car was over fuelling and it probably needs a remap. I took it to a local rolling road and they told me that it probably didn't need a remap as it probably has a fault like an exhaust sensor or injector.

The car is standard but has the centre pipe of the exhaust replaced with a straight pipe.

Has anyone ever had this kind of issue before or any advice?
 
Certainly seems like there is a fault, which needs rectifying before you start wasting money on remaps.
I assume the engine light isn't aluminated on the dash?
 
Injectors are prone to fail on Clio's. A friends 182 had the same symptoms as yours.
My 197 is running at 24mpg and running strange, so I've just ordered 4 injectors from K-Tec for £190.

Or

Try running some fuel cleaner through the system to see if it helps, but if I'm honest injector replacement is your best bet.
 
Thanks for the advice, I've been told !it might be injectors, o2 sensors and even a new cat today! I'm not sure if I should go down a diag machine or injector flow testing route first though?
 
Checking the cat will cost nothing, so I'd do that first.
You'd likely have real bad performance if it's blocked up or fallen apart.
 
lambda sensor has biggest influence on fuelling if its old it will be slow to adjust fuelling...
 
I've plugged in a diagnostic machine and two fault codes have come up:

P0300: Multiple cylinder misfire
P0313: Misfire with low fuel