Help Guys!! 1990 4x4 Problems.....

[Old Toy]

Hello to all of you, this is my first post and know there will be many more to follow. I have a 1990 Toyota 4WD Pickup with a couple of problems (ok maybe more than a couple but that's all we'll talk about right now), The Idle Air Screw on the intake keeps backing out causing the engine to "surge" at idle. What keeps the screw from backing out? Can I fix it? Also, first start of the day I drive about 2 miles and the temp gauge heads towards hot then slowly comes back down to 1/4 past cold. The engine is not actually getting hot, I know, I checked and could stick my finger in the radiator without melting it!! I replaced the thermostat and it still does the same thing, what causes this? I am thinking a temp. sensor needs to be replaced but thought I would throw out the question first.

Thanks,
Dan

[texas12]

Do lose that idle air screw! Mine backed out and I lost it. Took me 2 weeks to locate a replacement (someone on this site had an extra and mailed it to me). Toyota does not have them, comes as part of throttle body assy. If you take it all the way out, there is an oring around the top. It is either missing or worn out. Go to the local hardware store and find a replacement oring. That should keep it in place. Or the poor man fix, get a piece of duct tape and tape over it!
Temp guage thing sounds about normal. Engine heats up with thermostat closed (higher temp reading) and then thermostat opens lowering temp. If it is not staying high or overheating, I would not worry about it.

[Old Toy]

Temperature gauge goes almost all the way to hot before it does start to come back down to normal though, it never used to do this and kinda gets me a little excited at times........