seriously surges at 3rd gear

check fuel pressure, check for vacuum leaks, hoses disconnected, etc. clean throttle plate with chokecleaner first.

I have checked all hoses are Ok, cleaned the throttle plate but no solution. I will add that this happens in the morning but goes away after 15-25 minutes of driving.

then check your coolant sensor for being bad. what was fuel pressure it may not be high enough.

I just realised that if I let this trooper warm for 15minutes I will not have the problem of surging/hesitation in the morning! The ,mechanic told me the fuel pressure was ok. Where exactly is the coolant sensor? My temperature gauge is always on cold. What else do I need to check?

I don't have access to show you where the sensor is but check your thermostat, it may not be working and stuck open. if yyyou hav eone of thoseinfrared sensors thermostat thing you push abutton to fin dhtetemp yo can stick it on the upperhose to see what the tempis it should be around 210 or so. if your check engine light isn't on then your sensor is probably ok.

Is the nut with red in it the sensor? See one of the pictures.

i can't really see what you are talking about but from the pic you better cleann that battery terminal and replace the bolt going through the terminal or get another one. i'll send you the coolant temp sennder tommorrow when iget back home. but you may need to replace the temp sender not coolant sensor. you realy neeed to see what the temp of the engine is as well. the poor battery connection may be some of your trouble that you are having as it's the ground.

My trooper also doesn't have the check engine light on the dash. Sample attached additional images;
Wiring is also a mess and it doesn't have the O2 sensor like other troopers I have seen on the internet on my research of the problem

you may have bad valve seasl for the using oil part or the heads are plugged up and not draing back down, easy enough totell by pulling valve coverif you see a bunch of crap all over it's gunked up. I'm sending two harness drawings which tells the color of the wires and where they go, not much else help with this. Or you could get a another harness off of same year truck with same engine. I am taking this that it's a trooper and not a trooper !! with a2.8l engine. Otherwise this will be wrong. temp sender is third pic, actually all sensors

Hi, I sorted out the surging problem by readjusting the electric choke (making it leaner) on the carburetor. The surging was being caused by the fact that the choke wasn't opening up fully (as supposed to) until after 20minutes or so of driving. Im in Africa and we have very good weather and it doesn't get that cold. I can now start the Trooper on a cold morning and within a minute of warming up drive off with full power without the previous hesitation/choking. I am now working on solving the oil consumption problem. Additional help and suggestions are welcome

you really should check your pcv system to make sure teh pcv valve is working, that will cause oil consumption, but you should get a leakdown test if you have a mechanic that knows how to do that around you.

I have observed today that this 4ZD1 does not have a thermostat and is running with pure water! What are the implications of this and should I proceed and get a thermostat and why?

actually you need athermostat because with pure water your coolant sensor won't work right. it will leave thetruck in open loop all the time. It may be a reason for oil consumption as well so ya put the tstat in and use 50/50 antifreeze mix. this will take ethylene glycol or the green antifreeze.