cylinder 3 misfires could it be the timing belt?

Generally speaking if the timing belt skips you'll have problems on all cylinders, I'm not too familiar with tercels in this regard, but I think you're on the right track checking that cylinders systems first... You've already checked spark... Check compression, the injector, and fuel pressure

before removing the injector run some injector cleaner through the system. check the ignition timing anyway. but ya i'm thinking it's the injector as well. in my opinion ur toyota has seen it's last days as ur daliy driver. so go have fun junking it. id put it in a 4 cylinder class demolition derby lol.

it couldn't be the timing belt cause you wouldn't be able to start cause the timing belt is use to synchronize your first wich is "#1"spark at start up,it could be a defective spark plug"wiring".

this cars after 15 years of use begin whith this problems the piston rings begin to allow oil to passtrough and this oil get spark plugs wet, if timing belt skips maybe the car dont start. in my case y have to change piston rings to solve a similar problem

I have a 1991 Tercel. Had the same problem. It started out idling really rough on warm days then just got worse over time. I replaced the plugs, wires, cap and rotor and had no change. I then replaced the injector and it ran like a champ. It was an easy job that took about 20 minutes.

You have checked all the first things to check correctly. You could check fuel pressure next but if it was weak you would have issues of low power all the time or stalling. You can easily identify what cylinder is dead by pulling the spark plug wires to each one and noting any change. The cylinder that has no change is the misfire. If your car has an electronic plug on each injector unplug it and check and clean any dirt off the electrodes, including the wire. Make sure the grounds are also good. If thats not the case you may want to take it to a garage to have the injection spray checked. Injectors do wear out and are subject to being clogged up from small debris and varnish that does get thru a filter. Before you take it in try adding a full bottle of high strenth injector cleaner to a low fuel tank, Let it work thru the system. This will free up and disolve any varnish that has clogged the injector. If the cleaner doesnt solve any issues try a new injector. Should only be $30 or so. Dont buy a used one unless its a rebuilt. If that doesnt solve you issues you may have a stuck valve(s) witch means taking the valve cover off and seeing whats going on up top of the engine.

its the timing belt, check to make sure all your marks are crank and cams.

i personally am a chevy man , I love my sb chevy 327 , brilliant !!!!! but i will tell you the problem right now and you need to listen to me and everybody that says the same thing " its your timing belt " somewhere along the timing lines. I just bought an aftermarket harmonic balance pulley which the timing grooves are in it also has a woodruff key , so what do I do when i get it , I know one thing I didnt do i didnt check the timing marks like a dumbass and just checked the woodruff slot and bolt holes and had the same symptoms right away and you can put 2 and 2 together long story short fix your timing and car will run like a champ , I will skin that