So now you think the fuel side is ok what about the exhaust side? Restricted exhaust, blocked cat, split flexi joint? Is the compression good? Are you losing compression from a glow plug? Valves sealing? Cam wear? Or is it sensors cutting back the power? N75 valve?
Engine earth faulty? Battery faulty? Battery connections loose or corroded? Alternator faulty?
Thanks for the ideas.
Just whipped off the cam cover and it looks fine with very little wear on the cam and/or rollers at all.
There's no leaks on any of the glow plugs either.
Started up and checked Cylinder Deviations with VCDS, all are sitting at around 1.5 which is higher than expected , with one negative and the others positive. Looks like there's some compensation going on to try and balance the fuel flow across the cylinders. Does this point to injectors or is it a symptom of other issues?
Although there are no leaks on the N75 pipework, my thinking behind this is that it modulates the watergate, using the boost pressure for the signal, so as long as the wastegate actuator is not mechanically broken, ie stuck open, then the N75 will only come into play when boost starts to build. I do get some boost when revving it, but the response from idle is really poor, with very low power, almost as though it's in limp mode, but VCDS does not show any errors in the engine ECU.
Cranking is fast, with defined compression strokes, so I'm sort of ruling our any mechanical issues in that sense, but I don't have the ability to check pressures. The battery is less than a couple of years old, and earthing has been checked and cleaned.
There's only the exhaust to check now, is there an easy way or do I just remove the fixings to the turbo and blow down, or use hoover to check flow is not restricted?