What would cause two of the cylinders not to work?

either the spark plugs in those two cylinders are bad or the wires from the distributor to the spark plugs is bad.

define not work... Are you not getting spark on two cylinders? Are you not getting compression? What exactly are you experiencing? How do you know 'two' cylinders aren't working?

Are you dragging 2 cylinders or what is the problem? If that is what is happening then check your spark plugs, wires, and distributor. i wouldn't drive it like this for too long because the gas will keep building up in the cylinder and wont have anywhere to go and will eventually go into your exhaust and smoke real bad or it can go in the intake which is bad.

check the distributor cables and plugs.

stop right where you are and take it to a professional, obviously you are in over your head and need real help with this one LOL!

anyway... the following could cause a miss in a cylinder: wrong plugs/end gap, burnt valves in the two cyl, worn or broken rings, dirty dist cap, burnt plug wires,dead injectors........the list goes on and on. so i would check for spark at the plugs,then pull all the plugs and do a compression check, then if you find a hole with no compression i would then do a leak down test to see if it is rings or burnt valves, also test those injectors with a diode and see if they are firing(this is why it is important to include a good description of what else is going on under the hood.....makes it alot easier to find the problem) good luck with that!

check to see if a fuel injector wire came loose

I have an 02 ranger 3.0, (notorious for problems) anyway I started having a misfire, changed plugs, wires, coil,pvc valve,fuel injectors,upper and lower intake manifold gaskets, valve cover gaskets, cam sensor/syncronizer,throttle possision sensor along with a couple other parts, anyway even punched out the cadis,. Then did a drop down test after it still ran bad. Well cylinder 2 & 3 aren't holding pressure. The more I read up on it, Ford are notorious for bad heads. Wish I would of known this hundreds and hundreds of dollars ago.

2000 2.3 engine with new coil packs, new plugs, new injectors, new plug wires, engine rebuilt timing belt on time . still running rough can not gett ti to run like it should. the engine was built at a local machine shop. need advice as to what to do next.