Lubed

Your engine is port injection, the intake valves remain clean by the fuel wash from the injectors. One less job for you.

It pays to double check TDC on No1 cylinder using a screw driver down the injector hole. Are the three lines on the cam sprockets facing each other? Its normal for an engine that's been standing for a long time to have low compression, compression soon ramps up again after the engine has run for a short period if all engine components are damage free.

Good work.....broken the N46 Voodoo. Even little 4 bangers can be rewarding to fix and bring back from the edge.

Check that you have power and earth at the high stop plug connection, if that's all good then it must be a light fault.

Short trips of only a couple kms is torture for any ICE, condensation never has a chance to evaporate and the oil gets contaminated very quickly with fuel, moisture etc.

"MAKE THE N42 GREAT AGAIN" you have my vote. Making these little 4 pots sweet again is not as hard as some make it out to be.

Once oil/coolant leaks, chains/guides, valvetronic motor, stem seals have been been sorted it will be a sweet little engine again for another 100000 + kms. These engines have their flaws yes, but once looked after are underrated.

No, there is a specific service function that needs to be carried out with a diagnostic tester.

Did you teach in the valvetronic end stops after replacing the valvetronic motor ?

The N43 does not have valvetronic, so one less system to fail, that's a positive

Reading back, the Dealership offered to diagnose the issue on the day. That offer was turned down by the owner of the car due to other commitments. What do you propose? the dealership doesn't give the keys back like you would a drunk at a party?

That's a big accusation, every story has two sides. What's yours?

I would hazard a guess that rings don't fail overnight. Sometimes on engine shutdown the crank can spin backwards a few degrees due to a piston not quite reaching tdc on the compressor stroke. The compression then pushes the engine backwards, if the timing chain is worn then the chain jumps a couple of teeth.

I'm struggling to understand how a engine running perfectly at shut down one night, then come the following morning the piston rings have failed causing major compression loss and the engine not to fire. Is it worth getting a second opinion from a different workshop or doing a little more investigation yourself? It does not seem like the root cause of your problem has been identified.

A competent mechanic should be able to have the rocker cover off and check the cam timing in 2hrs. With the N47 having a track record of chain issues, it would be high on my list of things to check.