Technical Misfire/cutting out!

[vfourracer]

Just performed a routine check over yesterday afternoon under the bonnet, checked all the electrical bits and fluids etc. Since then the car has developed a slight misfire whilst idling, and a bad misfire every - so often, it completely cut out twice today.
I have changed the arm, cap and plugs, as they were all looking slightly grubby, and will get round to changing the leads, but were done not too long ago.
The only other thing would be coils, but it idles perfectly other than the slight glitch, which leads me to believe the coils are fine.

Any ideas?

Thanks people!

 

[Deckchair5]

Most likely the plug leads as it happened after you moved them and that's often when they give up the ghost. Stick a multi meter on them and check each resistance. Should all be about the same. Check all the plug leads are on tight

Make sure there's no dirt tracking lines inside the distributor cap, that it isn't cracked and that the brush isn't worn down too far. Check the contacts inside the cap and see if they've corroded badly

A good check to do is look under the bonnet with engine running when it's pitch black and see if there's any electrical arcing happening. Power's got to go somewhere! Sometimes a plug lead will be arcing to earth, easy to spot in the dark

 

[Trancendental]

Is it a petrol or Deisel?

Carb or Fuel Injected?

My 1.6 Single Point Injection (carb) was doing a similar thing the other day, was idling at random and stalling when stationary.

The Jet on the side of the carb was faulty, a quick modification at my favourite Fiat garage and it was fixed, literally in under a minute.

The fault was also causing the car to over run when switched off, the jet is controlled electronically and is meant to initiate when the ignition key is turned to the off position. it cuts the fuel flow to the carb but when its faulty it either fails when you switch off and in my case was initiating while the car was running. Also caused the police to follow me and pull me over cause I was stalling everytime I tried to stop.