2004 Punto 1.2 16V 4 door.
New Plugs and air filter. New Cat and 2 new lambda sensors. Nudging 60k miles.
On cold damp starts seems to run on 2 cylinders.
Engine light flashes then comes on. OBD finds P0300 (Random misfire) P0304 (Cylinder 4 misfire) & P0302 (Cylinder 2 misfire). Other warning light comes on; Car with Padlock picto in dash, something to do with anti-theft?

Thing is, when I drive 3 miles, cup of tea at my mum's, start her up, runs brilliantly on all 4, very zippy.

I'm thinking moisture is getting somewhere and then drying off?
Engine loom?
Coil packs warming up and don't like the cold?

I'm at a loss; anyone have a roadmap to fault find or sen this themselves?
Plus, worried about unburnt fuel going into exhaust and ruining new Cat; is that a worry I should have?
Thank you.

The cats are fairly durable.. you probably have a hesitancy.. not TOTAL FAILURE on 2 cylinders.

The padlock . Immob

Is a weird one..

Pointing towards basic power supply.

Run a new battery to engine cable.. GP section FAQs for more info.

Charlie

The old Cat was rattly as a box of bolts, broken up inside and must have been obstructing exhaust. Ran great for a while with no faults and does so even now after a warm up. I checked 2 earth points from the battery to body in the engine bay, they looked ok but took them off, wire brush and put them back. I'll have a look at GP section, bit of a newbie, need to find out what GP section is. Thanks for feedback.

Grande Punto
The main earth cable can break down internally