Oil leaks from hose from turbo to intercooler on a Navara D40

black smoke is not enough air for the mixture
the intercooler hose swelling up when the turbo cuts in indicates a blockage in the intercooler or air inlet into the manifold
with a blockage ou will get black smoke so check the intercooler cores for blockages

Check the seals on the intercooler, for oil to get in the pipes means that the seals are damaged and its loosing compression

Unless you do your own work there
is no economical solution,the car has
to be properly repaired

Leaking of any fluid is not normal. The only time any fluid should expel from the car is if you have overfilled something. Your turbo could need replacing, you could have a hole in the intercooler. Have you noticed any lack of performance or extra smoke...

If oil is accumulting inside the inetercooler, it means that the turbo-shaft seal is leaking causing oil to by pass in to the intake system, then through to your intercooler. A quick check to see if this is a fault, remove the hose/piping from the turbo the intercooler and place a piece of white paper over the hole at the turbo where the air is dispelled. Run the engine for a few minutes and if you notice any oil occuring/building up on the white papaer, then it is the turbo seal. This method is used on everything from jetskis to dump trucks. If no oil is present then the oil leak will be coming from somewhere else on the engine, and being sucked in through to the top of the intercooler. May have to remove it to see where any other leaks are coming from.

are you sure the correct amount of oil is in it? if over full the engine is trying to drag the crank shaft through the oil

U have a serious turbo seal failure problem.

take off pipe going to the intercooler from the turbo see if oil is found and clean then other pipe from incooler check it .if oil is found .drain oil in intercooler .you have an oil leak from the turbo this is why you will have light on far left of dash

Sounds like you need an O2 sensor. You need to have it scanned, places like AutoZone will do this free of charge.