Just been down to read the faults codes and it came back with 3, surprisingly though none of them relate to a misfire even though there's still a fair amount of engine vibration.

17961

17912

17500

Which after having done a brief search all seem to relate to air pressure/vacuum leaks.

Edit 17550 not 17500!

Edited 8 October, 201510 yr by Chefdave

17961 (P1553) MAP/Baro sensor Range/Performance problem, causes:- intake/exhaust leak, EGR system, Evap canister purge valve, Throttle body, wiring or MAP/Baro sensor

17912 (P1504) Intake system leak detected, Causes:- Intake leak, EGR system, EVAP system, hose connection(s), Throttle body

17500 ????? doesn't show on the list in ElsaWin or Autodata manual ????

Sorry I meant 17550

I wonder if changing the hose linking the throttle body and brake servo has had any effect

How can I check for all the things these codes mention? I'm screwed!

17550 (P1142) Load calculation Signal low, Causes :- Throttle body, MAP sensor, APP sensor(pedal position sensor)

If you have VCDS you could look at the sensor signals on it's vagscope facility, but air leaks etc, get a long length of plastic/rubber tubing stick one end in your ear and then systematically go around all of the inlet manifold/throttle body and all the pipes attached and listen for a "hiss"

Thanks once again nige, yes this weekend I will attempt to search for a vacuum leak as the codes are pointing me in this direction. If necessary I'll purchase a plumber's gas canister too.

I think I'll clear the codes, give the engine bay a good visual inspection and then do my best to find a leak. Then I can re-scan to see if it fires any codes back at me.

I've also been recommended a local firm who supposedly specialise in diagnostics so I'll give them a ring tomorrow too. As I'm inexperienced even a simple vacuum test takes me ages. Maybe they can speed things up.

Edited 8 October, 201510 yr by Chefdave

An update on the thread as I got the car back from the mechanics today, complete with brand new MOT with no advisories. I didn't think this was possible a month ago!

So it looks like I fixed the misfire after all by changing and cleaning the plugs/coils/injectors/brake hose etc etc. However the mechanic believes that I managed to overwhelm the ECU with too many changes too quickly and it just couldn't cope. It stalled about 10 times on the short 2-3 mile trip over to the garage when I dropped it off, this is how badly things had deteriorated.

I don't completely understand what he did but he spoke about resetting the baselines so the ECU had some reference points to work from. A Hi-tech reset I suppose.

A big thanks to Nige who took a personal interest in this case, even coming all the way down from Milton Keynes to help me out. Cheers Nige!

I'm not completely out of the woods yet though.

We drove it around the block so he could see that I was happy with it and as we pulled up the Engine Management Light flashed up. It was related to an oxygen sensor; an entirely new fault code. He cleared it and said it if reappears I may need a new one as its possibly the result of the unburnt fuel that ran through the system while I had the misfire. When I pulled up to the lights on my way home from work the engine felt a little shaky too. I'll have to see how it goes.

If its still OK in a few weeks from now I may end up selling it. This has been my first venture into the world of VW and German cars and its been a disaster. Maybe I should stick to Fords from now on.

Edited 28 October, 201510 yr by Chefdave

Hopefully the final update on my thread.

So after months and months of intermittent misfires, misdiagnosis and god knows how much spent on fixes that didn't work it turns out that the underlying problem is either burnt valves or worn piston rings. Looking at £750+ to resolve it which I'm reluctant to pay considering how much I've come to hate the car.

It has 12 months MOT so I'll probably stick it on Autotrader and take a massive loss. The advert will be transparent so I won't be passing the buck on to somebody else. Its been a very expensive lesson, one I won't be repeating on either German cars or poor research. I'll probably get slated for that comment but I've come to the conclusion that they're over engineered, unreliable, expensive to maintain pieces of junk.

On balance I'd prefer a beat up fiesta, at least I wouldn't be worrying about it as much.

Thanks to everyone for their help, especially Nige who spent a great deal of time on this case.