Took my 5er out for a little camping this past weekend. After towing (weight: 8000#) for about 20 miles in 80+ degress, and coming to a stop, the truck would idle rough and low at times. It stalled once at a stop sign in the campground. It doesn't do it all the time, but once in a while and usually while running a low speeds (under 10mph). It was only during the low campground speeds that I noticed it. Also when I first start it would do it on occasion. Once I rev the engine a little, idle always returns to normal.

It has done this a few times before even when not towing (AFTER all below was done)

Thoughts? Where can I start the diagnosis? How to proceed item by item?

New Motorcraft parts in past 6-8 months:

1. Plugs, wires, cap, rotor,
2. PCV, air, and fuel filters
3. Thermostat (192 degrees)

Plus several othert things that shouldn't be the cause (ex. radiator, hoses, etc).

Thanks!

 

....anyone??

 

Base timing where is should be? Engine vac strong and steady?
If so first suspect for me would be the IAC, it should be open and ready to take over if the throttle closes completely/suddenly, ready and able move freely to react quickly to maintain normal idle speed for all conditions.

 

Good fuel pressure?