Well, with the help of a local specialist we finally got to the source of the issue.
After a couple of stints working away from home followed by a holiday, I eventually got the car into a specialist. After changing just about every sensor over the last few months I was expecting something major, but my issues seem to have been caused by a dud connection on the VVC unit. He disconnected and cleaned just about every connector in the engine bay, and once put back together it fired up and idled like a dream.
I've been using the car virtually every day over the last week, and she's performing well with plenty of grunt and no hiccups. Its just a shame that she's fixed in time for the rain and cold weather!
I’ve got someone coming to look at the car in the next couple of days with the view to completing a compression test to rule out anything there.
I did manage to get the stepper to settle around 26, but there’s still a hint of a miss at idle which makes itself know under sudden load. I’ll try to capture this on video tomorrow if I get the chance.
The fuel filter was replaced shortly after the issue started, but are there any checks I can do on the fuel regulator before looking at a replacement?
The plugs looked fairly consistent when I checked them last week, so it sounds like a compression test is the next course of action. I’ve already checked the inlet piping and can’t see anything obvious.
Despite having fairly amateur mechanical knowledge, like you I prefer to stick with tried and tested diagnostics but this car has me stumped! I haven’t checked/replaced the lambda or cat yet but I suppose issues there would reveal themselves in the MOT result.
I bought the car with an inheritance as a bit of a gift to myself, so more than anything I think I’m just disappointed that my seemingly well looked after example is proving so troublesome! ☹️
Tried the suggestion on the Land Rover forum, and apart from the obvious change in process the result is the same. The best way I can describe the idle issue is that it never seems to settle, including the stepper position. Took the car for a long-ish drive and the misfiring under load is still there.
The plugs and leads were only replaced at the end of last year and look to be good quality and ok in condition. Short of replacing these again, I'm at a loss as to what I can try next. Unfortunately, the MOT is due this week and I suspect that it'd fail on emissions if tested as is.
More adjustment on the idle screw this evening, and it’s still no better unfortunately. To add insult to injury, I wanted to top up the washer fluid (and check the battery connections just in case) only to find that the bonnet release isn’t working.