continuity of the wire, dirty sensor

Look at the highest point of throttle body. There is an adjust screw. (It might be covered with a cap.)

remove the cap and turn the idle adjust screw clockwize. count your turning degrees because you might want to put it back where it was.

and you should first ground the idle/timing checker and have a warm engine

then when you get it to 700?- check the timing

1989 5 door montero 3.0 auto
stock original Japanese
about 200k miles