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Just helped out someone over the WE with their rough running tdi, having come to me after spending over £500 with vdubs, who didn't diagnose it right! I said I'd be happy to stand up in court to tell them them what i thought of their 'professional' skill level. Huh! They changed the EGR valve. Wrong! I reckon @Rich, @Blue Loop, @Skajme or @RAB would be able to diagnose it in under 5 seconds. Took me about 30... Symptoms were obviously misfiring, running on only two cyls. until warmed up. Started ok, and had a loud tapping noise- really loud with the air inlet duct removed. VCDS showed a big injection quantity imbalance between cylinders at idle- trying to add fuel to cyl 1 and pull from 2 & 3. Obviously air starved on no.1 with the inlet valve not fully opening. It's amazing how vdub ECUs actually measure the rotation time between injection pulses and trim the injection timing to achieve a smooth idle. When a power stroke has more push than the other cyls, it obviously takes less time to rotate. So it adds fuel to the weaker cylinder and pulls from the others to try and even out the power strokes. Neat idea. This 2001 Lupo had 165k miles on it, with a decent history... Down to the breakers yard to grab a camshaft (and a tappet) from a 9N Polo, which was pretty much like new still. It always seems to be the lobe next to the pulley that goes, having seen a few worn cams at the breakers. The engine is at a slight angle, with the gearbox end being slightly lower. Straight forward job- just loosen the timing belt and tensioner. Pop off the valve cover and bearing caps. Pull the dodgy tappet. Pop off the pulley, swap over everything and back together again. You don't even need to remove the high pressure fuel pump or adjust the injection timing as everything is precision made.

Posting a few pics here of my recent clean up of the inlet plenum, air restrictor 'trumpets' and intake manifold on my SDI. (I know there's a thread on this but the pictures seem to have gone missing from the image hosting site, so here's another thread with pics if of help to anyone.) As others have said, I couldn't believe how coked up the trumpets and the intake vents were. Doused the intake manifold, plenum, and trumpets in multiple rounds of carb cleaneer and oven cleaner, as well as jet washing the parts in the end. Refitted with a new manifold gasket. Before reassembly hoovered out the intake ports with a handheld vacuum cleaner to remove any big bits of carbon that might have become dislodged during the cleaning/scraping process. Applied the CCV hose mod to stop oil vapour being re-routed back into the inlet plenum, and did the EGR blank, inlet manifold flap disconnect, then took out for a spin to flush anything out. Once the engine warmed up I ran a can of Diesel Intake cleaner through the inlet plenum to try and shift some of the deposits around the intake ports and valves. (Debatable whether this has a huge effect, but thought it couldn't hurt to try.) Will report back once I've had a chance to run another tank through it whether it feels much different etc. Much cleaner at least anyway! Some tips I discovered that helped me: - Oven cleaner works really well! - Ring spanner makes a good scraper tool. - Face masks are handy for covering open ports to prevent stuff falling in - Removing the inlet manifold flap housing: It's a bayonet fitting that turns *right* to release it. - Blocked off the EGR vacuum using an M5 bolt, and a small nail for the manifold flap vacuum. (Leave the wiring connectors connected.) Plan is to install an oil catch can soon rather than letting the oil vapour vent under the car.