I recently purchased a 2004 f150 heritage with the 4.2 and 5 speed. Its currently got 110xxx miles and keeps throwing a p0455 code randomly, I changed the gas cap 4 different times with no luck, is this a common problem with these trucks?

 

https://www.samarins.com/diagnose/p0455.html

You have a large leak somewhere in the evap system, the gas cap is only one of several componentrs.

 

Looks like it's time to drop the tank and poke around.
hurray.

 

I wouldn't drop the tank just yet. Lots of lines to check since the tank is vented to the intake manifold typically through a charcoal cansister.

 

The purge control valve is under the hood right near the power brake booster.

 

visually it looks fine I dont see any broken or cracked lines going to it, thinking about it, the prior owner kept the truck totally full of fuel at all times, I wonder if he continuously over filled it and that has something to do with the engine light.

 

Unlikely.

Your best bet is to smoke test the evap system to find the leak so it can be repaired. Take it to a shop if you can't do that yourself.

 

One reason filling to the brim is a bad idea is that the charcoal canister can get flooded especially if you don't park on a level space. Had that problem with a car a long time ago. Wife was parking with the front down a hill after filling up and it flooded the charcoal canister. May not be relevant to your problem. Do the smoke test as recommended.

 

The PCM opens the Purge control valve as part of the fuel tank system test.
Code 455 is telling you there is a ' large ' leak detected, as part of the program Logic decision test for draw down limit failure.
Like hose cracked, rotted, filter fault, hole in tank, Vent valve stuck open, tank fill neck issue, rust hole in tank, even the pressure sensor. that does the sensing etc.. Could even be under a mounting strap as a rust hole.
You can't find what you can't see.
Testing is in order to find the location.
The Evap system is a lengthy and complex combinatiion of tests at differeing vacuum levels, limits and parts functions.
A large leak says it can't get to " first base " in the test sequence
You might even have sucess using a hand vacuum pump at different points sectional testing but that's of hand squeezing and watching the Gage on the pump.
Just a side note, I have done this on old A/C sytems to evacuate looking for leaks, then filling with Freon, to sucess.with the vacuum level pulled down to 30 inches in the system... Again, it's a lot of hand work but should work if your inclined to do so and adapt to the system connection point of test and be sure your test connections are tight..
Good luck.

Good luck.

 

Sounds above my level of mechanical experience. I think I'll just keep clearing the code with my ultragauge until it starts causing serious problems.

 

It probably never will, but if you ever have to get an emissions inspection it won't pass.

Symptoms:
You likely won't notice any drivability problems.

Read more at: https://www.obd-codes.com/p0455
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I had a friend who bought an old Volvo that was throwing that code, and she had to get it emissions tested. She took it in and they found that the charcoal canister was completely missing. Wholesale was over $200.

 

Get it smoked tested or have a tuner turn off the evap codes

 

it just passed texas emissions last month, maybe i got lucky.

I paid $500 for the truck so I really can't complain about having to put a little money in it though

 

i haven't found a tuner who will mess with the lowly 4.2, everyone thinks if its not a V8 its not a good engine

 

I just passed texas emissions. Maybe I got lucky.

For as little as I paid for this thing, I should have expected to put some money into it