1.9 TDI PD130 awx misfire and esp light on

[DraigDu]

Hello everyone, this us a bit long winded.

Hope everyone has had a good christmas.

I have the b5.5 estate, 1.9 tdi PD130 AWX and have been having troubles with a misfire and ESP light come on. It started a few weeks ago, on the A55 it stuttered quite hard, and the esp light came on, so i pulled over, engine off for 5, when turned back on it was fine. A week or 2 after that it did the same thing while out on lunch break, but this time it was misfiring and only running on 3 cylinders, again esp light stayed on. Same day, finished work, started the car up, all fine, 10 minutes in... same thing again, but this time the misfire has stayed permanent and the esp light on permanent. After some research (not alot) all that I'd read up on it pointed to injector wiring harness, so i replaced that, no difference at all. Disconnecting the glowplug for cylinder 1 made no difference, on cylinder 2 made it cut out so definitely cyl 1, next thought was the injector itself, so i replaced the injector on cylinder 1, closest to cam belt, it run fine for 20 - 30 seconds then back to square one, stuttered, esp light on and misfire. I've had the multimeter out, checked the connections on the injector for continuity, done a voltage check on all harness connectors, all at 11.8v, checked glowplug, reading 11.6v, pulled glowplug out, in pretty good condition, no oil or anything, got continuity to the tip. Next step was the fuel distributor duct on the head, so pulled the injector, turned on ignition so the fuel pump primed and pressurised, have got fuel coming through to the port so there's no blockage, i don't think it's a gasket because I've only ever topped up coolant once and no oil or anything on the glowplug. I've had code readers plugged in and nothings coming up, no other lights apart from esp light. I'm hoping someone can point me in the right direction and had same issue resolves.

Sorry for the long post.