Delica diesel '98 space gear 2.8 turbo diesel. We are second owner 180,000 km. Problem is black exhaust when first starting up and then once accelerating between 80 to 100 km/ph no smoke. When decelerating black smoke again. Also when decelerating a clang clang clang noise is heard and it get sluggish till it has speed again. Have religiously changed oil and maintained other basic parts and fluids. Took it to a mechanic but they couldn't fix it. Wondering what is the problem.

Question edited for clarity
Question moved to Mitsubishi.

Yes no problem. Try it. If you need an octane boost, add a gallon of gas or 20 gallons.

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black smoke = excessive fuel = bad injector tips , low injector pressure , turbo not working properly
take the car to an accredited diesel specialist professional for a pump pressure and injector pressure test, injector calibration and tip replacement

turbo problem-check actuator to change blade angle in the exhaust side to the turbo that assists with directing exhaust gas flow onto the turbine wheel
could be problem vacuum vose or control module

Which area and country are you in?

Hi there a Particulate Filter is a device fitted to diesel vehicles that remove soot from the exhaust gases exiting the engine, they are normally located under the vehicle between the downpipe and back box.Hope this Helps

the turbo is a variable vane type
that means that there are vanes in the exhaust housing that redirects the exhaust gas flow onto the turbine blades to get extra boost at low rpms
those vanes are controlled by an actuator and vacuum hose from a sensor
the hoses get brittle from the heat and fails , the vanes can rust up and seize or the actuator doesn't get the message from the sensor
run the fault codes first , then take it to an accredited turbo professional shop for a proper diagnosis

I assume its the 6.0L diesel...If so sigh......double sigh.. I had one of these...triple sigh. I need a bit more clarification. How many km on the engine/vehicle. Also, you say that it blows black smoke while running at a constant speed at 2600 rpm, or while you are accelerating to 2600 rpm. Also, when you say the boost goes down, does it decrease by itself, or when the throttle is let off. The boost naturally goes down when the throttle is released (not trying to be a ****, i dont know how much you know). However, if the boost is going down by itself, while the engine is under load (its not supposed to, it should stay constant) it could be a couple of things, which "can" contribute to black smoke. If there is a leak anywhere from the turbo to the intake of the engine, it will cause the engine to get less boost, which means less air into the cylinders, which means black smoke. Check all of the connectors/tubing coming from the turbo to the intercooler, and from the intercooler to the intake manifold and see if there are any problems. The more costly problems which results in boost going down, and black smoke, deals with a problem with the wastegate on the turbo (controls how much boost is produced, and when too much is being made, it will bleed off excess pressure). So if your wastegate is malfunctioning, your boost will go down and you will get black smoke cause the engine is not getting enough air. also, around 160km...80mi, the injectors "can" start to go on the 6.0L diesels....I would check the turbo for leaks, the tubing for leaks, and the intercooler for leaks (a big rock can punch a hole in radiators and intercoolers...intercooler will be in front of the radiator). I hope this helps

65 thousand isn't much for a diesel engine.
I would not be too worried if it is only when you first start it up.

Diesel smells like oil at the best of times especially when it gets on your hands :) I have an old diesel engine (280,000 km never had the head off ) with no fancy turbo or anything on it. It used to blow a cloud of black smoke when I started it in winter time. It used to crank more before it started when it was cold too. The problem turned out to be 5 out of 6 of my glow plugs were broken. So it was just squirting more and more diesel into the cylinder before it generated enough heat to start. When it finally kicked all the fuel burnt at once hence the black smoke. There is a way to test your glow plugs (assuming you engine has them) with a multi meter. Or just get a mechanic to check and replace them as needed. Mine were about as complicated as changing a spark plug.

This is just my experience. I'm sure there are other reasons your can might be blowing black smoke.

Fuel pump: The vehicle is sensitive to fuel starvation caused by a clogged in-tank filter. (1991-96)