anyone know where to start with this problem, or how to fix it?

 

is it an evap leak? large? if so then if you ever had your truck runnnin with the gas cap off itll do it. thats all i know of to be a simple fix

 

it has only thrown the code a few times. i was getting "tighten fuel cap" across the cluster. so i replaced the gas cap and that didnt fix it. sorry i guess i should have explained alittle more. so anyway im figurin i have a leak but where do i start to look for it? what do i look for?

 

will a evap leak cause your ltft's to go rich but not affect your stft's? my ltft's are running between -4% at idle with the p0455 cleared from the computer, and -11% when the code is thrown. someone had mentioned doing a smoke test on the evap system.

anyone know how to do this and can walk me through it?
where can i get the smoke test kit?
what bout o-rings for the fittings? (cause that is probably be the problem right?)

 

you could take it to the dealer and let them smoke it.... otherwise a smoke machine is $$$$$.. sometimes you can get under there see residue from the leak, but not all the time.

 

It'S A LARGE LEAK, TRY CHECKING YOUR HOSE CLAMPS ON YOUR FILLER NECK AND OR IT COULD MEAN YOU HAVE A BAD SEAL AT THE MODULE , YOU COULD TRY PUTTING SOME PRESSURIZED AIR THROUGH THE EVAP LINES AND SOMEONE HEARING THE LEAK BUT IT'S A PAIN

 

Im bumping this thread because im having the same issue has anyone else experienced this and how did you fix it thanks in advance..

 

I have it as well. I've done so many mods to my evap over the years I figured it had something to do with that and haven't had the time to look into it. Mine also throws -11 to -16 LTFT on bank 1 often and has a hessitation at low rpm cruising and accellerating. When it pulls fuel on the LTFT my wideband will show in the 16:1 range on bank 1. Never really thought about the evap causing it. Haven't checked into it. With most of my shop in storage from my move I don't even change my own oil right now.

 

I also had a "Tighten Gas Cap" message so i just went ahead and bought a new cap but the SES light is still on Im gonna try disconnecting the Battery for a few hours this weekends to see if it turn off.

 

there is a evap vent back by the gas tank. i talked to a couple of buddies that work for a chevy dealer and there is a part that relocates the evap vent. they claim that the oe setup gets filled full of crap and screws **** up. so i bought it and replaced it and have been code free. sorry i dont have the part number anymore, but any dealer parts counter should know about it.