Technical Misfire occurred suddenly.

[Steph3071]

Just getting home from a 4 hour drive on some very hilly terrain and I noticed the car had started to run rough and clearly misfiring.
Any attempt at an Italian tune up results in the engine management light coming on.For a few seconds after starting the car it idles smoothly, but soon returns to lumpy idle.

I put it on MES and get

P0300-98 - Ignition failures recognition - Component or system over temperature.
P0303-98 - Cylinder 3 ignition failures - Component or system over temperature.
P0300-92 - Ignition failures recognition - Performance or incorrect operation
P0303-92 - Cylinder 3 ignition failures - Performance or incorrect operation

Restarting when cold doesn't resolve the issue.
Switching a plug wire didn't move the problem to a different cylinder.
Pulling the plug wire for cylinder 3 and leaving a gap for the spark to jump gave a nice loud crack as the coil fired for cylinder 3.

I've ordered some spark plugs, but not convinced this will cure the problem as it idles fine for a few seconds on initial start up.

Anyone got any other suggestions?

 

[Steph3071]

Moderators, please move to the correct Punto thread. I posted in the Arbarth thread by mistake! Sorry.