Hi Gareth
My original garage replaced the crank sensor, and then cam sensor, and then gave up.
The audi specialist i went to replaced both the crank sensor (my original garage had fit a useless cheap one apparently) and the glow plugs.
This has solved the issue with glow plug and esp warning lights, the car now starts fine and idles well, and performance is restored.
The car is now apparently fine, except for the engine light which came on. I took it back to the audi specialist with it being so soon after their repairs. They confirmed it wasn't the same issue and that all their equipment was pointing at the egr valve being on its way out / clogged up. This didn't surprise me as I do a lot of short journeys and the car had been in garages for a month with lots of short test journeys. However, they realised on removing the part that it was actually in full working order and not worth replacing, so they put it back on.
Since then, still no light. But their advice was that the fault readings they're getting point to a problem with the intercooler.
My question to the forum is whether it's worth trying a 2nd hand unit, or not? Is it worth persevering? Is this a sign the car is now becoming unreliable?
I'm not a mechanic and usually trust my local garage. The specialist I used next has excellent reviews. I feel like they did the right thing, and this fault is new.
But I'm not sure. I know cars can be a pain, and wish I knew more, but just wasn't sure what to do next.
Cheers
Jon