No, most of my woes stem from what looks like a faulty turbo. There's a horrendous reluctance to accelerate (dangerous, especially pulling away from busy roundabouts!), even the aircon puts a heavy drag on the engine. Something I can't define also doesn't sound right. Often a bit of a rattle accelerating.
So I've done some investigation, error codes P2562 (permanent, turbo valve position copy signal, not enough pressure) and corresponding P0299 (temporary, turbo pressure too low). Very occasional error about stuck EGR valve but that looks like the exception (one thing I do like is the historic appeared/disappeared fault log going back thousands of miles).
Turbo electrovalve replaced, no change. MAF, MAP and temp sensors all cleaned, EGR removed and thoroughly cleaned, seems to operate properly, front of the inlet manifold cleaned of oil and EGR gunk. I've removed the position sensor from the back of the turbo capsule (tip: file a tapered hex hole into a wingnut such that a screwdriver bit can be inserted, then it's dead easy to reach down and remove the sensor from the top of the engine bay!) The sensor resistance varies evenly from ~0-5Kohm. In situ, engine off, position reads 25% (I've read elsewhere the resting position should be 11-13%?) Engine idling, and the position is around 30% and barely alters as the car is driven.
If the sensor is operated manually, the readings do vary from 0 to 100% the further the sensor is pressed. At idle (and for that matter, most driving conditions) the electrovalve reads 100% and regulation status = "controlled turbo". Interestingly, when the sensor is depressed at idle beyond 50%, the electrovalve begins to reduce from 100 down to 0. So it looks like it would be impossible for both readings to ever track each other very far? Occasionally when driving hard the status changed from controlled to "regulated turbo" but only for a moment. I'm not sure if that's only because the call for turbo pressure happened to match what it's stuck at and all other times it's in some failsafe mode? (no engine light on).
My gut feeling is the vanes have seized. I see the vacuum capsule + sensor has its own part number (0375PO) but unsure of cost or if there's any way to test whether it's the capsule or the vanes seized. The effort needed to remove the turbo (and thus probably, just the vacuum element) looks considerable and probably more than I'm willing to do. It's unclear just how much work is involved getting the turbo (or just the vacuum capsule) off these cars. I think I'll visit machinemart Sunday for a vacuum test kit, but given the sensor doesn't seem to read below 25% with the engine off my guess is this is more than a lack of vacuum.
Does anyone know in detail how this system operates? Should the vanes default under no turbo to max boost, or the other way around? Should the electrovalve and copy sensor readings closely match each other at all times? Is there some sort of set-up procedure if the vacuum capsule on the turbo is removed and replaced? It's tricky working out how something ought to work, when some part is broken!
Another oddity, when the engine is revved, I can hear something 'squawk', like some actuator moving, almost a painful rubbery sound, then back again as the revs drop. It isn't EGR or the vacuum operated valve on the inlet manifold, but I can't really see what else would move.
