Outer Limits 4x4 Board

Hi guys, 3.9 V8 D1.
Just returned from a 2500 - 3000 km trip to Fraser Island and other parts of QLD. Upon returning, I've found the dieco running very rich and surging when warm idling.
Can this be a faulty MAF or oxygen sensor?
Any ideas on what the cause may be?
Thanks in advance.

You do not have o2 sensors.
If the MAF is dead or the connector is dirty the 14 CUX will go into limp home mode which is quite rich.
Try cleaning the small hole inside the MAF with some computer contact cleaner, and twist the male terminals in the connector a little tweak with long nose pliers.

If it then works the computer will revert out of limp home on the next start up.
A second place to look is the ECM temperature sensor which is on the top of the inlet manifold at the RH front, just behind the thermostat body. It has an injector type connector.

Check that the resistance is about 300 Ohms at normal hot temperature, and clean the connector. Your temp GAUGE has not changed position has it? If yes (down) the thermostat may have died and the engine is running cool which causes the injection to richen.

If none of those things fix it , it will be something obscure like the fuel pressure regulator. Just to be safe check that the vacuum pipe is still on it and not split.
Regards Philip A

Thanks. I'll check all those things in the morning. Temp gauge is reading as per usual.