I have a 2013 Fiesta 1.0 ecoboost which is prone to misfires and or loosing power during the warmup phase, e.g. first 5-6 miles. The car has only done 50k miles so should have plenty of life left. The problem is intermittent, some warmups no problem, others the symptoms can be anything from mild to severe. Its been to my local Ford main dealer 4 times and they have discussed with ford UK. Unfortunately despite many hours, part and cost the problem its not fixed. The story is too long to discuss here.

So I'm considering possibilities Ford might not want to tackle, e.g. carbon build up on the inlet valves. My question is, has anyone had the inlet valves cleaned, e.g. walnut blasted or by cylinder head removal and strip down? If so was it a success and what was the original reason for the work?

Thanks

Is it due for the cam belt change next year?

if it hasn’t already been done, i believe an engine out strip down is required, special tools required. Bear this in mind.

Personally I would have thought carbon build up would not be so intermittent.

Still on original cam belt. I bought the car at 3 years old and its been good up until recently.

Given you have a bit of an intermittent problem now, and that you have had it to a Ford dealer a few times and also next year you will need to spend around £1400 to get the wet belts replaced, I would recommend selling it now.

Now fixed. Turned out to be damage to the wiring loom. A metal bracket supporting the oxygen sensor connections had cut into the loom insulation and was shorting one of the fuel rail pressure sensor wires to earth. So, after many trips to the main dealer, new spark plugs, in tank fuel pump, fault finding hours, software update and finally a new PCM no fix. Instead, fixed DIY style, some things need patience and a keen eye to fix which isn't normally available at the dealers.