Truck Repair: 2000 F150 5.4 engine trouble, ford f150 xlt, ford f150

Question
My trucks (2000 Ford F150 XLT 4x4) check engine light has come on, no one is able to find the trouble. I have had the plugs and wires done,and the pcv changed...still nothing.The computer sowed the pcv as the trouble, but still no better after repair.The truck idols low, sometimes stalling out, it runs poorly at speeds under 70 km.This problem at first was only when the engine was cold, now it does it all the time, with very few exceptions.When you start the truck in the morning (I live in Nova Scotia) it idols up and down sometimes stalls out.Hope you can help....I have spent over $800 and still not working well.
Thanks so much,
Dar

Answer
Dar,
The temperature sensor is important for idle quality also, as well as through the complete range of operation.
The best explination I have is in the following discussion, and even though it is a Chevy forum, the sensors are about the same.

http://www.chevytalk.org/threads/showthreaded.php?Cat=0&Number=1366279

Van