Bighorn 3.1D idle issue when in drive or reverse gear

[luvB1gh0rn]

Hi there,
I have 1997 Isuzu Bighorn 3.1D 4jg2T auto. A few month ago, I stopped on traffic light and suddenly the idle was up and down (looks like it was hunting idle) and the truck was trying to go forward itself when idle was up. it same thing happen when reverse as well. when I put gear on neutral it shows normal idle range (750) and stable. It worse when heater or AC on.
When cold start, it has rough Idle for 2-3mins and back to normal idle (750).
Any idea what causing this issue??

Thanks

[Myarmila24311]

If the injection pump is in good condition, try checking the connection to the NP sensor located on the side of the fuel pump. In my case before, idle went up and down only, because the NP sensor did not work properly. If all sensors are in good condition as well, there may be an injector pump problem. Especially his governor.