If it's been running like this for a while then there could be other faults and issues with the engine (catalysts, uneven wear across the engine banks etc...).
Main issues are
1) Lack of spark - electrical fault
2) Fuel issues - in this case an issue with the fuel rail
On the M70 there was a similar issue, if a plug lead is shorting then the Motronic ECU will reduce or cut the injectors for the whole bank, unburned fuel kills catalysts so to protect the cats a misfire on 1 cylinder will cut the entire bank. I can only guess that the N73 may use a similar setup.
Fault codes may give a clue to what's happening.
If you are lucky then disconnecting all the plugs and lead and reconnecting them could fix the issue.