Have just purchased a 2008 2ltr diesel x type and runs beautifully apart from when I accelerate heavily black smoke from exhaust .Normal runnng no smoke at all and passed emission test for mot 3 days ago.

Can anyone advise likely problem please.

Sounds like a normal diesel to me! 😛

Seriously, diesels accelerate by overfueling as the amount of air entering the engine isn't restricted with a throttle butterfly like in a petrol. It may be it needs an Italian Decoke which would burn excess sooty deposits from the exhaust which can contribute to black smoke from the exhaust under aceleration and some injector cleaner may help too.

https://www.halfords.com/motoring/engine-oils-and-fluids/fuel-and-oil-additives/comma-diesel-magic-400ml-264671.html

I've heard good reports in the past few years about that stuff and used it myself about 20 years back in a diesel works truck.

If you keep your eyes peeled while out and about, you'll no doubt see someone giving a diesel the beans andyou should see a similar black cloud from their tailpipe(s), remember when comparing it to yours that it always looks worse in your mirror than from someone elses car.

There could be other reasons such as a previous owner has had it chipped, turned the boost up or similar, all of which would result in bigger clouds of black under hard acceleration while still allowing an MoT pass.