Persistent Evap Codes in a 2002 4.7 AC

Howdy, mates. I have owned this truck for 18 months, has 105K miles on it, runs like a top. I did all the catch up maintenance during the first year. Some weeks ago, I got a CEL with codes P0441 and P0446, evap leak codes. It’s been in shop jail several times and this is what has been done:


Replaced cracked and leaking hoses from canister to engine mounted valve assembly.


Installed new OEM gas cap.


Replaced the engine mounted evap valve, as smoke testing revealed faults.


Leak tested the evap canister, found pinhole leaks and a sticking control valve (part of the canister) – replaced that assembly.


Only OEM parts have been installed. Still getting the 441 and 446 codes and the truck continues to run beautifully, even with the CEL light on.


Do any of y’all have experience that might guide us in locating the remaining faults here?

 

Welcome to the club . . . I'm in the same 'Hurt-Box' . . . cool folks here will chime in to help.
It's all the smog crap.

 

Same here as well. Thought it might be related to the gas smell I get with a tank fill up.

 

Are we relying solely on what shop folks say and if so, do we know for a fact the gas cap is OEM ?
If relying solely on shop, have you checked gas cap and when putting it on, does it click when tightened ?
Do we know if shop cleared all codes and if so, how long did it take for these 2 codes to re-appear. ?
These 2 codes together normally point back to gas cap.
Have you double checked their work as far as vacuum hoses ?

 

Gas cap is OEM, and clicks properly. I have a code reader and verified no codes after picking up the truck. Took about 2 weeks for the codes to reappear. Hoses are new and tight.

 

I have seen a filler neck broken

 

https://www.youtube.com/watch?v=GAzOOWfje9o

https://www.youtube.com/watch?v=HjxMY78uNs8

These are both Sequoia related, but what I'm going to try if I ever get bored enough to fix mine.

 

Smoke test.

 

Those codes have not returned in the 12 days since I first posted this request. The only possible corrective action I took back then was to wipe clean the sealing surfaces for the new OEM gas cap, and did not detect anything much. Dunno, but I like not being haunted by the CEL.

 

I too was going to suggest looking at the fuel filler neck like @johnstansbury suggested. I'm assuming you got the truck pre-owned and depending on where it came from could be causing the leak.
It sounds like you may have gotten to the bottom of it (fingers crossed) but could be worth looking at if the codes come back.

 

Heh I’ve got 6 months before my next inspection. This is a reminder to start figuring out my evap issue again. I have gas smell by filler so perhaps the neck is leaky.

 

I've had to replace the filler neck and/or fuel tank on my past Tacomas for evap leaks

 

OK, I took y'all's advice to look at the filler neck.The hard parts are discontinued, but the two hoses are still available as OEMs, albeit pretty expensive. I found a 2002 takeoff complete assembly on ebay, so I became well familiar with it's structure. Very unlikely that the steel bits were suffering leaks, but my two hoses had clamps on both ends and were as old as the underhood hoses I already replaced for tears.

I took the take off assembly and two new hoses to my shop, where they replaced the hoses. I have not driven it much since then because I had a minor accident. It sits in the driveway awaiting a body shop appointment in January. Today, I ran it to burn out any condensation (used a bottle of Heet) and found the gas cap released pressure after a sit of 10 days or so. Good sign!

Thanks for all the tips, guys.