Hi I have a 57 punto 1.4 t-jet, purchased around 8 months ago and has been in the garage 4 times with an intermittent misfire on cylinder 1. At first the fault codes indicated the coil pack had blown, so they replaced it and it ran fine for a few hundred miles before developing a misfire again. This time codes pointed towards a dodgy fuel injector so that was replaced with another new coil and a set of new sparks. After this work was completed the car was running well for around 4 months until it developed yet another misfire on cylinder no 1. They have found that the sparks are gradually becoming wet leading to a loss of spark and then a misfire, they claim that this would indicate an over fuelling issue on cylinder no 1 however are not really prepared to investigate further as they have no idea of the cause. Hopefully someone can give me some possible causes for the misfire excluding the coil pack and injector (these have already been replaced).

Cheers,
Jamie

What about the other cylinders did they also check them out? they might have also have wet plugs.. just no error.
If all the spark plugs are wet i would check for a stuck lean O2 sensor... or even a exhaust leak before the O2.

The ECU should have the capability to adjust injection times on each cylinder.. but I'm not sure it does.
Maybe an exhaust leak on the number 1 cylinder could fool the ECU into over fueling on that sensor... but improbably because the exhaust gases are mixed together before the turbo and in the turbo before they get to the O2 sensor.

I would also check compression on cylinder 1.

Leaking injector ?