I've got a 94 with a 351 Windsor. About 3 months ago, it died on me as I was driving at a low rate of speed. After testing, I narrowed it down to the engine control module. A month later, it stalled out at died on me at a red light, this time it was fuel pump & filter that got her running again. However, I had a new issue where the truck, while in park only, was searching for an idle and couldn't find one. It would go from 1,500 rpms, down to 500, and right back up again. The check engine light came on as well. It would eventually find the idle but once I tapped the accelerator it would go back to searching. I narrowed it down to the idle air control valve. Through all of this, my father in law, who I bought the truck from, said that the gas mileage is not as good as it once was. The idle is much better now but while I'm driving at about 50 +/-, when I take my foot off of the accelerator, the rpms rise slightly and then go down to normal, then when I start to give it gas again, it hesitates for a split second. The check engine light is still on. I have an old Ford Mechanics OBD1 code reader that they used to use at the dealership. It gives me 3 codes. 10- which I understand to be "snap throttle" which means I have to immediately open the throttle wide open and release it for the scanner to finish the test, 111- system fine, and 179- fuel at lean adaptive limit at part throttle: system rich. These code translations are all from the Chilton's manual. When I looked online I found a different meaning for 179, Fuel system was rich at part throttle Single, Right or Rear HO2S - Fuel control. I have been debating on taking the throttle body off, cleaning it, and replacing the TPS. What does everyone here think? I'm not a rich man and can't afford to just swap a part out just for the heck of it. Lol! Thanks in advance!

 

I think you're on the right track. Clean the throttle body, test the TPS and also check out the IAC valve while you're in there.

 

In my code book your first interpretation of 179 is listed for cars only. The second interpretation is for trucks only. You may be looking at a bad O2 sensor. Your truck should only have one - at the 'y' of the y-pipe.
Check the wiring to it before you throw a new sensor at it.

 

10-4. I'll do that as soon as the dang rain lets up. Thanks for the quick responses!