Has the valve clearances on the Peugeot enging been checked? If it does not have hydraulic valve lifters, the valves will need periodic adjustments just like the older MB engines.

It could also be that the engine needs an overhaul or new or rebuilt injectors.

There is no such thing as a choke on a diesel. The idea of a choke is to create a richer mixture and promote vaporization of the gasoline by increasing the vacuum in the air intake system. Neither is applicable to a Diesel engine.

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