I'm hoping this is finally done on the Expo. STFT's and LTFT's were erratic and into the double digits during live data, and sometimes dropping into single digits. I've been getting both codes in the last few months, but more often (daily) and was doing everything to chase this issue, I was even going to get into the intake gaskets even though I doubted both sides would go out at the same time. With both codes, I was hoping it was before the intake and was a hard to find vacuum leak or a bad component.

I inspected and/or changed the following: all intake lines checked with vacuum for leaks and replaced all rubber at the "T's", PCV and elbow assy from Ford a few months ago ($36), checked fuel pressure and had a solid consistent 32lbs, FPR checked and pressure rose accordingly when disconnected, breather hose at intake from drivers side valve cover replaced, brake booster line checked out ok, IAT, TPS, and DPFE ohms all checked out ok. EGR functional test was good. I read about the dirty/faulty MAF, gave it a good cleaning and changed the live data values slightly, but the codes would return.

I decided to buy a MAF sensor, disconnected the neg cable from the battery and put it in this morning. Reconnect the battery and ran the live data. The values were a little high in single digits but dropping, probably the computer relearning? Took it for a 20 mile drive and the STFT and LTFT dropped to almost zeros and fluctuating in the very low single digits, so I think I got this issue put to bed.

My fingers are crossed and I'll report if the MAF didn't fix it. I'm the kind of guy that doesn't like to throw parts on the truck unless I get a code and the component checks out bad, I didn't get a MAF code but I took a gamble after all the research and I hope it payed off.

 

Just in the way of an FYI (but you maybe already know), the LTFTs are kept in a 3 X 3 grid (total of 9 cells). One axis is load (light, medium, heavy) and the other axis is RPM (idle, cruise, high). The scan tool displays which ever cell the engine is currently operating in.

Hope your new MAF nails it.

 

I'm just learning about fuel trims and will accept any advice and knowledge. It seemed like the LTFT's were more static but still dancing around 25%. I'm just glad that after I replaced the MAF the values changed dramatically to the good. If that didn't fix it, I was thinking smoke test next then possibly a diagnostic from the shop $$$$=ouch. Time will tell and I'll monitor the live data a few times a week.