Jackaroo diesel

If you have some time I have a tale to tell below which breaks down to 2 questions,

I have been driving the 4XJ1 turbo diesel for work since it arrived in the 1998 model Jackaroo. A few months ago we decided to buy one ourselfs and ended up with a 2000 model with 94,000kms on the clock. before we brought the dealer gave it to us for the weekend, did a 100+ km, towed our camper trailer and the car behaved perfectly so we brought it. The car had been serviced by the book except for the 90,000km service (4000km late) which was completed as condition of the sale. Now things get interesting.

2 days after buying the car we pulled out of the driveway and for the next 300m plumes (or clouds) of black smoke filled the view from the rear vision mirror and then it slowly reduced but still visibly blowing smoke. Rang the dealer and took the car back to the mechanic. Checked the obvious of the wrong oil but he swears in put 10w-30 oil and certainly the oil was nice and thin even when cold. The mechanic pleads compression engine ignorance so the dealer takes it to a diesel specialist. They say it blows a bit smoke, normal for diesels and the car is alright. Not completely convinced as the work jackaroos don't blow smoke like that.

Now the car starts to surge (very gently but enough for your head move backwards into the head rest) when below 2000rpm and the car is not under load. So when you are coasting in traffic in 4th at 60km or in 1st hunting for car parks at the shopping centre. UNfortunately this symptom is variable so it is hard to convince a mechanic of it. The surging problem continues to get worse and it is now time for 100,000km service. I tell my tale to holden (lots of blank looks) and when I pick the car up they say nothing is wrong. I'm dissappointed but as I drive home, other than a few surges when I leave the car park the car drives smoothly at all revs and the amount of black smoke is less, only really noticable when you accelerate hard.

Question1 Changing the oil is a miracle cure, can this be so?

Now, 1000km after the service the surging problem is still cured but the black smoke is returning even when you accelerate gently and now we get a lot of white smoke though this lessens as the car warms up. The only thing we have changed is to isolate the 2nd battery (& change it to deep cycle one) from the cranking battery to increase the power we have for running the camper trailer. The car certainly ran worse immediately after this but has since improved a little (less white smoke but still the black stuff as described above). I have taken the car back to the auto electrician and the electrics are good, not connected to any sensors and properly earthed so it shouldn't interfere with the car computor. The one thing that did happen was the battery was disconnected so the computer was without power for an hour or so.

Question 2 Could this be the cause of the return of the smoke (or just coincidence).

Sorry about the length of the tale and any advice would be very welcome

2scout

PS Any idea where I can find a diesel mechanic in the ACT area? I think holden are good at spark ignition engines but those compression ones are a bit of a m