1992 Hiace puffing black smoke

Hoping someone can give me some indications as to what could possibly be wrong before I take it to my local garage.

Since the warm weather is here, my Hiace Super Custom is running really rough. Its a 1992 2.4 Diesel Auto Super Custom. It runs fine when it is cold but the moment the temperature starts to rise the following happen

Its puffs out lots of black smoke (not grey nor white). It misfires and the tachometer starts to hunt ie goes up and down very quickly but does not stall.

When it is stationary, there is not really a problem when it is not in gear. There is a occasional misfire. However, the moment I put it in gear, the misfires get worse and there will be lots of black smoke from the exhaust. It even leaves sooty carbon on the ground when the exhaust fumes hit it.

When I am doing above 60 mph with the rev above 2000 rpm, the problem eases but the moment I take my foot off the accelerator the rpm starts to hunt and the dreaded black smoke appears with a vengeance.

Any idea what could be wrong?

Fuel starvation change filter add a dose of cleaner.
If it still does it suspect a gummed injector, any Diesel place should be able to diagnose and cure this for you.

Bob a mobile mechanic lives in Thurruck would be happy to help contact rcmvr@aol.com

Hi Clive

Many thanks for your response.

Have changed fuel filter and air filter when the symptoms first appeared. No change.

Even put it through Terraclean in the hope that its clogged injectors but no good.

Have emailed Bob quite a few times but he must be a really busy man as still no reply.

He is busy, if you can wait he will ge back to you. He is very reasonable on costs and knows Toyotas inside out.