Diesel engine speed hunting?

Evening. I drive a Toyota land cruiser 3,0 l turbo diesel, clocking 260,000km. It's a 99 model, pre commun rail engine. The engine speed is hunting +/- 150 rpm when idling. accelerating the idle speed to 2000 rpm does not change a thing. When driving at constant speed, I can feel the same ';hunting'; happening. happens when engine warm only. Any idea please?Diesel engine speed hunting?
I hope I understand what you mean by ';hunting';. Your Toyota engine is operating irratically possibly surging unevenly. My father operated Toyota diesel pickups on his carrier route for many years so I am a little bit familiar with them. They weren't turboed but there are still things that will make them do that. Check for air in your fuel system. Sucking air kills diesels. Make sure the fuel filter isn't overly restricted. Make sure your mass air sensor is operating properly because if they don't the computer will go into limp mode. Yours being turboed I am sure it has a wastegate which controls your boost. Make sure the vacuum lines are not leaking going to that wastegate. Make sure it is working because it can greatly affect your performance and economy. Last but not least make sure you have good fuel in the tank and no water. Some diesels run better if you put some cetane additive in with the fuel. Good luck.