My last ride was a 2H powered 75 series ute, which I turboed (and then some). When I bought it,(unmodified), you could load that thing up all you like and the only time it would puff black smoke was when you stab the throttle then it would immediately go clear again.
It could be a number of things,
Check your air filter,
Check your intake hose is not collapsing on acceleration,
Check your exhaust is not damaged (squashed or bent)
If all are ok then check these few things,
There should be two vacuum lines that run down from the throttle body to the top rear of the fuel pump, check that they are not hard, brittle and possibly leaking.
Where the rearmost line goes to the fuel pump, that is a housing that contains a diaphragm, this is your accelerator diaphagm. If it has a hole or cut in it or is visibly worn out, replace it. Also sometimes oil can get in there and give a false vacuum reading too. It will drain out when you open it to look at the diaphagm anyway.
Generally this problem will raise it's head as a high idle, running on between gear changes and be difficult to switch off in the severest cases.
If all of the above are ok it would seem that someone has wound the fuel up, probably hunting for horsepower that the engine simply does not have, as the engine can only inhale so much air.
Here goes..
On the back of the fuel pump at the top, there is the lever that is actuated by the EDIC motor (the thing that shuts off the engine). If you look at lever, there is a screw (about 10mm dia) that this rests against (but only when the engine loads up). At the back of the screw is a round lock screw that should have a twisted wire through it and crimped with a stamped lead crimp fitting. If this wire is gone, it's a dead give away that it been molested.
Try to gently unlock the nut with a punch if you don't have a suitable tool, I made one to fit.
Here's the important bit, turn the screw
IN (clockwise) for less fuel and
OUT (aniclockwise) for more, Important to remember, DO THIS IN 1/4 TURNS AT A TIME!!! and remember to lock the lock nut back up each time too.
Keep a note of how far you have turned it in case you need to return it to the original point at which you started.
Hope that is of some help
Rowen
PS. Turboing is easy on these engines but I found it a little tricky to tune for highway running as the engine would hunt, mainly due to the fact there was no wastegate in the set up. To tune these properly they really need a boost compensation device and they are quite dear to buy. I am at the moment toying with another non wastegated 2H turbo, using check valves and flow restrictors in the vacuum lines so as to not require one. I will post when I get it sorted.
