2.5td smoke on start up

My 90 2.5td starts fine, but blue smoke's a cloud and runs a bit rough for about 10 seconds - then it all evens out and runs fine except for the odd slight misfire and when it does that hiccup misfire the exhaust puts out a small chuff of blue smoke. If you drive off straight away a sensation of holding back intermittently happens, I suspect because its chuffing a blip of smoke again. After a few minutes this stops and it drives perfectly, pulls ok (needs cog down on hills but can do 65 no problem at all). It does not smoke once all these shannagans over, even when checking in mirrors/following headlights etc. If you stop the engine it will restart no smoke, unless you leave it for a while, the longer you leave it the greater the cloud.

which 2.5 td?

Defender 19j