Hi all,
I have a 2002 Renault Clio 1.2 16v that when the engine light, bottom right hand corner, isn't on it runs great, it pull's nicely in all gears up to 70+mph.

Then at idle the engine light flashes on and it runs rough, the plug on Cylinder 4, furthest from gearbox, is all sooty whereas the rest are look great, cylinder 4 is also 30psi down on all the other cylinders, there is a slight popping noise at the exhaust

I have changed the wiring loom that goes from the ECU to the injectors and that, due to it being chaffed a little bit, the metal cage had been removed before I got the car.
I've cleaned the throttle body, replaced TDC sensor, plugs and inlet manifold gaskets. I have also put Redex in the tank and cylinders, and placed sealant in the water system, with no effect to the compression. My brother in law who I got the car from told me he had the coil pack replaced, it's the block coil pack with the leads made into it.

I have also noticed the car heats up really quickly and the fan does not seem to switch on no matter how long the car is running, but the temperature gauge only goes to about half way!

I am running out of idea's as I am more used to older cars, but the only things I can think of is Temperature Sensor, Lambda Sensor, a sticky or burnt valve, a crack in the head or an air leak somewhere.

I am getting a OBD2 diagnostic tool tomorrow, so hopefully that will help, but is there anyone that could help I would be very grateful as this it driving me mad.

Cheers
Ian
Norfolk