2006 Expedition XLT with 5.4 3 valve, 155+ miles.
Put gas in the Expedition last weekend, then ran it through car wash.
While leaving car wash check engine light goes on.
Scan it and see P0442, small leak.
Check gas cap and cleared codes.
Start truck again next day, check engine light again.
P0442 and P0446.
A couple days of driving and clearing code, now constant P0446.
Tried checking gas cap over, put some silicone spray on the seal, blew a little compressed air and carb cleaner towards to "check valve" on underside of cap.
Planing to get a new gas cap this weekend.
With the luck I have, I thought I would see if there is anything else I should look over or prepare for.
Seen a few links and videos showing work on the pump and solenoid for the emissions system.
Wondering where the pump, solenoid, and tank are for this set up.
Anyone else had any issues with anything besides an old faulty cap at all?
Just trying to check into other possible causes before I play around and change the oil this weekend. BTW...hearing a lot of clatter lately and trying 15 w 40 diesel oil for first time instead of 5 w 20. Hoping it will quite things down a little.
As always appreciate the help and advice
THANKS ! ! !

 

Your fault code(s) indicate that there is a leak in the evaporation emissions system. Short of guessing, the ONLY effective way of troubleshooting the system is with a "smoke test" whereby smoke is injected into the system at low pressure with the two valves (purge and vent) properly closed and see where the smoke comes out indicating the location of the leak. Typical leaking points might be anywhere from the gas cap to any of the connections on the top of the fuel tank to the canister and its valve to the purge valve under the hood or any of the tubes or hoses in the system. There's quite a lot of plumbing involved.

If you're going to guess, you might as well guess that it's the gas cap or its seal since its a common wear item. Make sure the sealing surface of the filler tube is clean and free of corrosion, dirt or damage. Try a new Motorcraft cap. Reset your codes and drive it for a while and allow the EVAP monitor to run and see if it passes or fails. This monitor is often pretty tough to get to run so patience may be necessary.

FWIW, this is an emissions-only situation, it has nothing to do with the vehicle's performance. Unless you have an impending e-test, there may not be too much urgency attached to finding and repairing the evap leak.

 

Thanks !!!
Fingers are crossed for the gas cap.
Especially since I had just filled up prior to seeing codes.
Will keep the rest in mind and dig further if that doesn't get the light to stay off.
Been clearing it daily for a week currently.
Truck does run fine, just rather not see the light even though I know what it is.
VERY much appreciate the help ! ! !

 

For my own info too...
The gas cap is supposed to allow atmosphere into the tank, but nothing out into the atmosphere, correct?

 

While there can be a leak, a stuck purge or vent valve can also cause the code to pop up.

 

The "evap assembly" which is the cannister and a solenoid and such is located above the spare tire. If the new gas cap doesn't solve it, you can remove that assembly from the truck and test everything to see if it's all in good shape and the solenoid valve works as it should. If there's no issues there, then it becomes a bit of a pain in the ***, since you'll probably have to lower the gas tank to get to all the tubes on top of the tank. A smoke test will help locating the issue.

 

I seem to recall that, at some point, gas caps with a one-way inlet check valve were replaced by sealed units and the system then vents inward via the vent valve and the charcoal canister. Someone feel free to correct my foggy memory, if you have the correct details.

I do recall that on my old SHOs (89-94), I could test the one way valve in a gas cap in a bit of a nasty way. Clean it off, then stick the small end into my mouth, seal the threads with my lips, and try and breath in. Effective but nasty, like I said.

 

Which would, of course, be considered to be a leak since it was supposed to be sealed at that time.

The canister vent valve would be more susceptible to this since it's exposed to the atmosphere where bugs and spiders can get in and make a nest or dirt or mud can end up getting into the hose and into the valve.

 

Remove the spare tire first and you get a whole world of room to move around up there.

 

You are correct, when vehicles started becoming equipped with emissions controlled charcoal canisters (instead of vacuum controlled) manufactures switched from vented to sealed gas caps

 

Not if the valve were stuck closed.
That aside I think of a leak more as a broken/cracked fitting or hose.

 

Wait! Let me get in on this, also.

A stuck open purge valve would cause a lean condition (P0171/174).
A stuck closed purge valve would appear as a leak because there would appear to be no measurable vacuum at the tank sensor.

 

Hmm...are those questions or statements? I'm assuming statements since there were no question marks at the ends.

 

Was not lucky enough to be able to fix with just replacing the cap, but did get it taken care of.
Started changing my oil yesterday (in freezing mid teen temps-cause that is my luck also)and thought I better look for obvious stuff before just buying a cap and crossing my fingers, experience has shown that rarely works for me.
Checked out the stuff I knew was related under the hood and on firewall. Nothing jumped out at me. No big vacuum leaks, broken hoses, or such.
When underneath I started following lines, hoses, and wiring from top of tank.
Got over the rear end and it's supporting "cross member" and see a piece of small diameter corrugated wire loom that has a sharp 90 degree bend and a spot of wear right through.
A little tug and pull and sure enough it separates and one of the two leads inside breaks.
Dropped the spare tire got some better access and see some pretty nasty looking pinches and rub spots covering a couple inches of both wires.
Spliced in a couple pieces and cleared codes.
All good.
BTW...first time using the thicker 15w40 diesel oil really quieted things down.
I have always been hesitant knowing there has been some debate as to good and bad of using it, but have to admit it is nice not sounding like it is coming apart. It was getting bad enough that I was worrying, but after 60-70 miles of driving yesterday, not silent but not enough that it gets your attention at least now.
Sorry to muddy up my own thread...

THANKS very much for all the help, tips, and advice.
This place is and always has been AWESOME to me for that ! ! !
Appreciate it again !!!

 

Let us know how things work out after you've driven it a while and allowing the EVAP monitor to execute.

An electrical circuit fault would be expected to post different fault codes than the ones you pulled and reported.