Ford Repair: 97 Ford F150 XL, vacuum leaks, intake leaks

Question
I have a 1997 Ford F150 XL with a 4.6 triton V8....the best way that I know how to describe the problem is that after I crank the truck and start driving when I take it out of gear it goes below idle speed and dies....everytime I slow down or stop it just dies-shut down. Everyone I have asked has said that it is a throttle positioning sensor but before I went out and spent about 100 bucks to have the Ford place put it on a machine I was wondering if you could tell me what you think it might be. Thanks William

Answer
Hello William,
    My first step on that problem would be to closely check for vacuum leaks, air intake leaks between the MAF and the throttle plate, bad PCV valve, or dirty throttle body. If there is no diagnostic code for the TPS circuit, it won't likely cause your problem. If you have any diagnostic codes, always look for a possible cause for those first. An engine misfire at idle from either the ignition system or being too lean or improper mixture(problems mentioned above , bad MAF, low fuel pressure) is the most likely cause of a sharp engine drop. If no signs of any of those thing are found, replace the idle air control valve. It is hard to get to because it is mounted all the way to the rear of the throttle body adapter. If that valve is stuck in one position, it wont idle properly. It is likely that is your problem if there is not any air leaks etc.
    I hope this info helps, and I'm very sorry for not getting back to you sooner. Good luck!   Shaun.