Punto sporting engine missfire

[petrolhead55]

Hi folks . just new on the site and would like to start by saying hi to all. ok here goes .
My Punto sporting Yplate is missing slightly on acceleration and i have changed the plugs ,leads and coil pack and its still doing it .
The management light comes on when its driving but if its just idling it goes out , my code reader says there are 3 codes as there are cylinder missfires in cylinders 2,3,4 . any ideas what the prob could be folks .:bang:

 

[jug]

head gasket leak, which is not uncommon.
failing that i would think the timing belt has slipped, but HG is more likely.

 

[phil j]

If the engine management light is coming on it could be the cat?

 

[beau]

could try unplugging lambda sensor, i had similar symptoms, and it was that, doesnt cost anything to try! so nothing to loose.