2010 F150 w/4.6 Have been chasing a rough idle in drive with the AC on for some time now, and when I change plugs they looked lean. No codes initially, checked for vacuum leaks etc, etc. I'm a decent shadetree mechanic but could find nothing. This week, come home after a round trip of about 250mi, taking my gas tank down to about 1/4 or less. Get out of the truck and I hear snapping and banging under my truck. Look underneath , and my plastic gas tank is nearly imploded, sucked in like an empty drink bottle. From other forums,have read about this problem..turns out, the solenoid valve in the charcoal canister that vents/filters the fuel tank fumes had failed. Apparently, there is no fail safe mechanism, so the constant running of fuel pump, sucks all the air out, none can get in, so it implodes. Now for the dodge the bullet part, some have had this happen to such an extent, that the sending unit for fuel level was damaged and some have suffered pump damage as well, resulting in hundreds of $ in repairs for a $60 solenoid failure. This solenoid failure can also contribute to a lean condition, so I'm hopeful for this as well. If you have an F150 and it seems to idle rough in drive, especially with AC on or you suspect a lean condition, check this valve first. I believe it's official name is the canister purge solenoid valve, was $63 from my local Ford dealer, as none of the chain parts houses had stock...they were more expensive anyway. AT least at the moment, it appears there was no damage...so far
