Emissions Problem for MOT

[pccapri]

Hi, my mk1 fiesta has failed its MOT on emissions. They are according to the machine 3 times over the allowed limit. Ive changed the carb over and its stil too high, i have noticed that its getting harder to start when cold and also kicks out a lot of black smoke when accelerating. Im thnking piston rings may have gone, but im hoping for a quicker fix or something else to check first. Has anybody got any ideas?

[escort21]

Black smoke means massive overfuelling, if it was rings it would be blue smoke. If its overfuelling it'll be hard to start as it'll be flooding, try starting it without the choke and it'll probably start ok. Adjust the mixture screw when the engines fully warmed up by winding it in until the engine starts to run rough then turn it out again until it runs rough and the correct setting will be in the middle 

[pccapri]

thanks for that, ill have a play later. Ive got a Colortune so that should help.

Would it also be possible for the valves to be wearing due to not enough lead replacement in the fuel? I got one of the lead drop it in the tank thingys but not confident its working properly.

[escort21]

If the valve seats(only on the exhaust side) were worn it would cause a slight loss of compression which would make it more difficult to start but due to your symptoms I dont think its that. In my opinion those lead things are a waste of money. To be honest ive never had any of my engines valve seats done, you'll have to do a lot of miles before you'd notice any problems, sort your fuelling out and i'm sure itll be fine.