i need help - i live in VA, and all repair shops are closed on weekends, and i need my truck asap... the code 0456 has been on for about 6 weeks - small evaporative emissions leak. the truck ran fine, so i didn't think much of it. this am, truck started to ride ROUGH and stall out while driving - i made it home, but BARELY. would a small emissions leak result in this? i rechecked - 0456 is still the only code being thrown. help?!?
thanks!

neil O.

 

hmm, mine's been throwing 0456 and 0440 for months, and mine drives fine. i think something else is up with your rig.

 

yeah, thats my guess too, esp since "major evaporative emissions leak" has its own code, and its not throwing that. any other thoughts on how i can diagnose the problem if a code isn't being thrown?? nothing looks out of place under hood/undercarriage...

 

When does it die. Idle? driving down the road? Need more info.

 

it started to drive rough enough that if i wasn't 1/2 mile from home, i would've had to pull over. it felt like a 98% clogged cat... however, i've had that happen before (on another vehicle) and it seems that a clogged cat is more of a gradual loss of power, whereas this was a very sudden and extreme loss of power/rough sputtering. besides, no code thrown to indicate anything wrong (besides 0456). it sputtered back home, i parked it, and now if i cut it on, it idles so rough that i can only assume it will cut out after about 5 seconds. i only tried twice while parked, and i cut the engine off before it had a chance to die...

 

Try a new gas cap and check the canister lines next tot he fuel tank..see if that helps.

I'd check the fuel pressure and see if the throttle blade is moving freely on the throttle body. Take the volant off and have someone give it some throttle. Could be a spark issue too...you're not on the original plugs are you?

 

yeah, original plugs... 76k miles. also, original cat. yeah, i figured new gas cap for the 0456 code, but, this seems much more serious than any problem that could arise from a small emissions leak (i think). still confused as to why no other codes being thrown...

 

Wow, those plugs are supposed to be changed every 30K. You are over twice the legal limit. Sounds like your problem.

 

Legal limit ...you drinkin again lxman?

I'm thinking the evap code and the rough idle/stalls are a separate issue. DTC's aren't accurate at all and a lot of major problems won't even throw a code.

 

my dad has an 02 quad cab 4.7 and had the same problem. he took it to the dealership and got the "throttle position sensor" changed. guess that was the prob... cuz it hasnt happened since