Military Vehicle Repair: Diesel start up smoke, isuzu trooper, glow plugs

Question
Hi Ron
This is diesel question which has stumped my garage, I'm
hoping your wider knowledge might help.
The car is an Isuzu trooper 3.1 turbo diesel 1992 135000 miles.
Ignition is no problem, but whilst it is warming up and idling it
misses ignition in one or more cylinders and "coughs" white oily
smoke, if I rev this gets worse.
After a minute or two these symptoms subside and it runs fine
warmed up.
The car has spent a month being looked at with the following
work done.
Fuel injectors cleaned, fuel pump replaced,and glow plugs
checked.
The mechanics are a bit baffled and are suggesting checking the
valves can tou suggest any other likely causes ?

I know this is not precisely your vehicle area of expertise, but I
thought your wider knowledge might prove valuable.

Many thanks for your help if you find the time to get round to
this request.  

Answer
Hello Andrew well Im not to knowledgeable on import diesels. Im not to sure of the systms they use,but it kinda sounds like the glowplug system isnt working correctly. Im not sure if theres a glowplug controller or module on this vehicle or not.That would be were I would start. Sorry couldnt be anymore help.