Ford Repair: 97 F150 5.4L, vacuum leak, o2 sensors

Question
The engine light has been on for some time now, but just recently my trucks really started to hesitate especially after it warms up and I'm trying to go up a grade, I've replaced both O2 sensors and had Auto Zone put their handheld diagnostic meter on the truck they read a Po171 code, I think its a coil problem because a few years ago I had a similar problem, but I don't want to replace them all. How can I figure out which one? if you agree with me.A second problem is my wipers stop for a few seconds in the middle of wiping the glass when their on intermittent only and then they'll start up again and repeat. When their on slow full mode or fast their fine.
Thanks for any help you can give me.
Rick

Answer
HI Rick thanks for asking.
If I remember correctly P0171 is a that bank 1 is running to lean.( Not enough fuel) This could be due to a blockage in the fuel system, maby a plugged injector. It could be a vacuum leak, exhaust leak, I dont think the coil will have anything to do with this problem. There are many possiblities to a lean code, It will have to be hooked up to a scanner that will check all the system peramiters to see waht is not running in spec, One thing to look for is the fuel trim in the data stream. If it over 15 percent then there is a definit vacuum leak, this is the most common to lean codes. Another possibitly is The evaperatovie emmisions control system, This this is what contrlos all the fuel vapours from the fuel tank, The fuel vapours are let into the engine to be burnt so it doesnt go into the atmosphere. Theses are only possabilities, it is hard for me to say what your actual problem is without looking at the vehicle. Now with the wiper motor problem i think it will be one of two things, either one of the windings are gooing in the motor. or there is a bad ground from the motor. Inspect the wiring that goes into the motor for any breaks or even lose wired, make sure there is a good ground for the motor, is all wiring is ok then you are probably going to be instaling a new wiper motor.
Good luck
Chris P