Toyota Repair: 1982 toyota pickup 22r skips/backfires after engine warms up

Question
Good morning Ted. I have a 1982 Toyota half ton truck with the 2.4l 22r engine. 289k miles, 5 speed manual trans. the issue im having is that after the engine warms up, it starts misfiring/skipping/backfiring. If i hold the throttle wide open it will straighten out momentarily, then start doing the same thing again. i have been told that it is prob the ignition coil. i have recently replaced the water pump, fuel filter, plugs and wires, and air filter. I dont want to just start randomly replacing parts if I can help it. Any help is appreciated.

Answer
Hello, you didn't mention distributor cap and rotor, if they were not replaced I would recommend doing so. It could also be a distributor problem and yes, the coil could also cause this, using an ohm meter check the resistance of the distributor pickup coil, should be about 1000 to 1800 ohms with engine hot, this used to be a common problem, check coil resistance, positive terminal to negative should be low about 100 ohms , positive and negative to the high voltage terminal should be high, around 15,000 (15K) or more