Have a Volvo kid 300. Charger works fine on warm up and when up to temp.
But if in gear or neutral the rpm dies slowly from 1500 plus down to 500 , over a range of time ,and also a
range of times as to when it starts.
Fuel is fresh and there is no restriction in the fuel supply.
Even when engine is at its worse, there is a good flow of fuel down retun pipe back to tank, the same
all time.
The only thing that is a funny sign, is that the engine smokes slightly ,diesel smoke when it’s left to get really low rpm.
while the fault is happening.
Then turn off and restart immediately or later. The problem as gone and the whole thing stats again.
Im pretty famiular with the kad engines have had plenty problem with them over 20 years. .
ant ideas. Also no fault codes on diagnostics., and have calibrated all controls .