What's next?

this is regarding a 2001 taurus sedan 3.0 liter 116,000 miles.
She developed an intermittent starting problem. No particular time or situation to when it would do it.
Had it diagnosed as a crankshaft sensor which was replaced. fixed the start issue but then had a noticable missfire or jerkiness to the car while accellerating. I was told it could be fuel filter so replaced that.
After getting it back it still had a very noticable jerking to the drive. Was next told it might need injector cleaning. Yhe exhaust sensor light would come on at times. So it was suggested to change an injector in cylinder 1 as that was the problem cylinder. Not sure if that has fixed the problem as I have not yet got the car back as there was a problem reinstalling the tank that required parts from Ford to fix.
If I get it back and it still misses what else could it be? I was told maybe a valve for that cylinder, does that say the end is near for this vehicle?
Any ideas?
Thanks

You have not provided any real history on the car. A “miss” can be a bad spark plug, or a bad coil. You car has COP’s (coil on plug) meaning each spark plug has an ignition coil sitting on top of it. The coil has a spring with a rubber boot that connects the coil to the plug. The plug can go bad, the coil can go bad, the rubber boot gets old dried out and can allow the electricity to arc to ground so the plug won’t fire.

When was the last time you had new spark plugs? Are the original coils still in the car? Have the rubber boots ever been replaced? This car needs to be up to date on all maintenance, then if the miss continues you trouble shoot if from there.

A valve problem would show up in poor compression, so you could have a compression check done to see if any cylinder is showing low compression.

I believe that car has ONE coil pack sitting on top one of the valve covers. It should be staring you in the face when you pop the hood.

Exhaust sensor light . . . do you mean the check engine light? That’s just a warning to you that something’s wrong which is causing increased emissions and that it needs to be diagnosed.

I’m not sure what the fuel tank removal has to do with cleaning the injectors.
As far as I know, your engine has a test port on the fuel rail. That is where most mechanics would hook up the fuel cleaning solution.

Number 1 injector is under the intake plenum, which would need to be removed for access. Are you sure that isn’t where the shop hit a snag?

It sounds like your car had/has more than one issue.