OBD II P0455

[nlareau]

Hey AB, F-150 threw a code this AM driving to work.  P0455 Evap System Leak (Large).

Did I just spend $138 to find out I didn't put the gas cap on tight?

If that's it, I'll keep the Autoscanner and count myself a lucky man. 

[AB]

Possible....The list of culprits includes the gas cap or a leak in the top of the fuel tank where the pump assy goes in...Clear the code, drive it.  It may take from a few days to a few months to reset if you didn't find the problem.  The computer must go through a specific drive cycle to reset the emmissions monitors and that may not happen for up to 6 months after clearing the light.

[nlareau]

Erased the codes, now the engine is a little rough.  It'll be that way until it recalculates all the ECM parameters and stuff, right?  Couple of hours?

[AB]

Shouldn't be if you used the tool to clear the codes.  If you cleared them by disconnecting the battery, then maybe.  Usually the ECM will learn everything it needs to know within the first 10 miles of driving except for reseting the monitors.

[nlareau]

I used the tool to reset them.  Feels like if I run it a little it'll be OK. We'll see.

[nlareau]

Truck ran like crap this AM. Felt like it was missing a cylinder and smelled like it was dumping fuel straight out the tailpipe.

10 miles into the drive to work and it magically smoothed out and is now as smooth as ever.

Apparently erasing the codes makes it unhappy.