1990 Toyota truck 4x4 4 cyl cutting off and on coming down the road when hot.

i would look it to valve cover gaskets and seal had the same problem with a 2000 neon it would run realy ruff and just about stall out and it would not make it up a hill/ it may also be a fuel filter clogged or has a slight block im not a toyota person so those are stuff to look in to

Take a spray bottle of water. Mist down your plug wires, cap, and coil. Do this with the engine running. If you do this in the dark, you should be able to see spark jumping and snapping. You should also hear a change in the idle. If no obvious spark leak, pull your wires from the plugs and see if you have any loose plugs. I have seen that before. You may want to check all of your vacuum lines also for leaks. When engine is cool, start the engine and spray some carb clean on your vac hoses. If idle suddenly surges up, you have found the leak. Check your battery connections also. Other than simple checks like that, did your check engine light happen to come on?

I had the same problem with my 1990 Toyota 4x4 Truck. After awhile it got to where it would cut off and I would have to restart it a lot. Was able to adjust the timing with the screw a turn or half turn at a time and it would work just fine for awhile. For me the screw was coming lose all the time and readjusting the timing. I bought some quick tight and was able to fix the problem. It has been going strong now with no problems for the last 6 months. Turns out a few other people had a similar problem and was able to help them out.