A family member has an issue with their Ford Fiesta 2008 manual. It has a 1.6L Duratec (Sigma) engine. The car has an intermittent problem starting. It will show the signs of starting, then fade out and stall. Today I tried starting it and it started first time. Then after getting said relative in the car to discuss things to look out for (e.g. listen for the fuel pump) it then began exhibiting the problem. It felt like if I could give it a bit of throttle it should still be able to be started, but there was a complete disconnect between the pedal and the motor losing revs and stalling. I can only assume it's got a fly by wire throttle and ignores the pedal when starting. In discussion about the issue, it seems that it's not related to cold/warm starting, it can happen any time.
The car has also started knocking when lugging the engine in 3rd about the same time which I think cannot be a coincidence.
Does anyone have experience with this car/engine who could give some pointers?
It seems to have fuel pressure and spark, so I can only assume it's some sort of metering issue? I wouldn't know where to start to pull any codes, as I'm a 1990's Nissan person. Cam belt was replaced, but the issue existed before this. As a result I think the timing is OK as I trust the mechanic who did the timing belt to put everything at factory spec.

