Shifting problems for starters

Can not figure out for nothing my 93 4x4 ranger won’t shift out of 3rd gear until 80 mph and only when I take my foot off the gas but as soon as I push on the throttle to maintain speed it goes right back into 3rd any one please help any and all suggestions welcome can’t keep filling up for 60$ and only getting 174 miles out of a full tank it did dump all fluid out one time in my yard line popped off tightened it up and refilled fluid but same I traded for this truck would much rather have a 5 speed manual but hard to find one around here

Also idles at 13-16 rpms hot or cold got the set screw backed so far off it’s not even touching the throttle body any more

I would start by looking for vacuum leaks. A 25 year old vehicle is bound to have a few.

I sprayed eather around and on all vacuum lines around the intake and no change in the idle

Was you talking about the idle or shifting problem cuz I know some vehicles have vacuum lines to the transmission

Any vacuum leak, any where in the system would reduce the amount of vacuum available and let un-metered air in affecting shifting and idle. If you found no leaks at the intake try at the trans. Another thought is the trans modulator at the trans, pull the vacuum hose off it. if there is trans fluid in the hose or modulator, the modulator needs to be replaced. If it is sucking trans fluid through the vacuum line that can also affect idle.

Ok thank you very much I’ll try that in a couple hours once the sun comes up