I have a 2000 ford windstar 3.8 im having truble with cylinder#5 it has a new spark plug and a new fuel injector

SOURCE: engine misfires

You didnt mention having changed the spark plug wires, so that is another item that could be culprit as well. As well, it could be a coil pack that is not working properly.

I cannot recall at the moment if that model year uses coil on plugs or if it uses coil packs. Either way, if it uses a coil on plug set up, take the one for the #3 cylinder and move it to say #4 or anyone of your choice and see if the misfire follows

If it uses coil packs, there is likely one coil pack that controls two cylinders. In that case just swap the coil pack with an adjacent one and see if the problem follows. Pay attention to where the spark plug wires go because it will be an issue if you get them mixed up. You just swap the coil packs around.

I would, however, start with the spark plug wires if you have not changed them already.

SOURCE: engine code p0307 cylinder #7 misfire

It could be carbon deposits on valve seats keeping valves from totally closing. You can try getting you a can of motorcraft PM3 top end engine cleaner and get engine up to operating temp then remove one of the small vacuum lines from the intake and draw the contents of the can slowly into the engine.After you have drawn in the contents shut engine off and let it soak for about 45 minutes then crank it back up and let it run until it clears. Now it will smoke like a forrest fire while you are doing this so don't be alarmed,just tell the neighbors you are spraying for mosqitos.This may cure the problem. If not you may be looking at a valve job.
This can be verified with a compression test if this is what is causing it.

SOURCE: 2000 ford winstar sel update to problem

i had asimiliar misfire on my 2000 windstar.the first thing to check is a broken valve spring by taking off the valve cover the other is a o2 sensor bank 2 i believe is the downstream.if not the valve spring then either the coil pack or thecontrol module. either way it is fairly inexspensive

SOURCE: 2001 Ford Windstar runs rough.

remove the coil pack and look at bottom of it if it shows any cracks coil is bad very common on these vans if you have a noid light check for injector pulse on #4 if you have pulse and good blue spark most likely the injector is bad you have to remove upper plenum to get injectors out let me know how you make out

SOURCE: Misfire on cylinder 4 only when accelerating

coil pack