Today, my truck started to throw P0171. I checked the PCV Tube and just cleaned the MAF Sensor. Anyone got any other ideas if that doesn't fix it? It drives fine just idles a little rough.

 

Its difficult to visually check the tube, because even tiny faults will trigger a code, and the grommet can be split on the inside, where visual inspection cannot see. Try the brake cleaner test at all three endings of that tube.

I ran my own Propane test, then I had my shop run a smoke test, 'looking more for validation of my results, I guess. (I was spot-on, but it was my first run with my Home Brew Propane rig.

The PCV valve, grommet and tube (all Genuine Ford Parts)

 

Give me more info on the smoke test or the propane test.

 

The smoke test involves using a smoke machine. Will pump smoke into the intake at about 2 psi. The machine is typically used to find evap system leaks but is very usefull for other things. You block off the throttlebody with a cap then take any other vacuum line off and hook the smoke machine there. There is always a small leak at the egr valve and the throttlebody but is normal. There should be no visible smoke elsewhere. I have chose not to use brake cleaner or propane. Open spark anywhere and things will get interesting fast! Using either also you will need a scan tool to watch the fuel trim values long and short. If the leak is big enough the truck will stumble when sprayed by the leak.

 

Alright. Thanks for that info. Knock on wood everything in fine so far.