The attached are some plots from Forscan Oscilloscope ( Cylinder Contribution/balance + Fuel Rail & accelerator pedal position)  Do these look fairly good at pretty close to 1.0 ??   ( car is Focus 1.6 115bhp tdci)

I have an engine stutter problem  occurring frequently but not always. It is almost exclusively confined to the second half of the engine warming up phase. When fully warm the engine is fine and runs efficiently. When cold there is no stutter.

Engine has cut out or gone into limp mode several times when slowing as clutch dipped and foot comes off acceleration. This has produced Fuel Rail pressure DTC's PO194; PO193 and PO191 + PO2D1 Cylinder 3 Fuel Injector 'A' Offset learning max limit. These were not present at the time of running FORScan, each one it seems being a cause triggering an engine stall.

My garage, based on discussing symptoms, reckons almost definitely an injector wear problem, but warns may be uneconomic to repair. They don't think FORScan can reliably consider injector function.  They are probably right? but I find it hard to believe that if the ECU can manage the injector wear ( 140K miles) efficiently once the engine is warm, that it is an injector issue and not a duff data during warm up issue ...( e.g. such as the Rail pressure sensor ( which has shown some funny spikes unrelated to the pedal position/REvs). I am a biologist though!

So views welcome on whether FORSCan cylinder contribution/balance  can be used to say injectors should be ok.

cyclinder balance with Fuel Rail.pdf

From a quick look at those codes the first 3 are fuel rail pressure sensor related (?) the final is Cylinder 3 injector offset (or similar), by my very quick search.
So (sorry I can't make much of the cylinder contribution - and don't know how it is generated, graphs unless there is anything visible with cylinder 3)...
I'd first look at Forscan demanded and actual rail pressures and if any erratic results, check wiring and sensor powers, grounds and ideally oscilloscope.

I assume you have for no other reason that it is cheap and a first line approach, changed the fuel filter and checked for air leaks via bubbles in the fuel line?

I don't subscribe to just changing things but if they are cheap then that may be cheaper than diagnostic time and whilst I'm a tightwad, it may be better to get a quality part if appropriate only on the basis of data?

I also would not change injectors without clear evidence, therefore a leak off test is first line for that with, perhaps a focus on cylinder 3.

Sold our C-MAX to relative and they were told "set of new injectors needed" when the problem was fixed with new leak off pipes, hence my concern!
Based on the results of that the condition of the injectors may be assessed THEN depending on results could relevant injectors be swapped, corrections recoded and the effect on the fault codes assessed (i.e. does the fault move - injector? or stick - wiring?

Unless it's something else entirely: turbo/EGR etc but Occam's Razor seems relevant from the codes?

As usual, I can only say how I would start to look at it as a Physicist (teacher, actually engineer)  BUT, it is now Biology's Time!

 

Delay in responding as car as have been assessing since fuel filter change.

I am beginning to doubt myself that it stuttered a bit on the drive home from the garage after the filter change. If it did, it was in the 2nd half of warming up 10 mins after start up, so I presume not due to any remaiining air bleeding out.....and, rather, consistent with previous symptoms

Weather has been warm since and has not stuttered. 100 Mile motorway drive that I do most weekends  got 66mpg yesterday.

Week before 61mpg...but it was much warmer weather yesterday.

Also since change start up sounds different. There was a crank or 2 of hesitation sometimes before - but it seemed to be the starter motor hesitating as opposed to cranking without firing up. Now almost instant start up.....but it's been warmer.

So waiting for a few cold morning tests before concluding anything.