p0442 problem

[lidavef]

I have a 2005 4.6 4x4 with a continuing evap problem. It started a week before the state inspection (NY) was due. First I replaced the gas cap with new proper one. Reset computer and waited almost 2 weeks for the computer to cycle. Same code. Next replaced the Purge valve, cleared the code and waited about 2 1/2 weeks to cycle. Same code. Next, I replaced the Vent valve and waited almost 3 weeks (it gets driven at least 6 days a week). I just checked it and the same code is up again, but NO check engine light. Why wouldn't it set the CEL? Also, it looks like the previous owner replaced the fuel filler pipe. Any ideas? Thanks.

 

[TechGuru]

Need to get the EVAP system fogged to find the leak. I have the code too but luckily I live where emissions are not checked.

 

[lidavef]

I actually bought a smoke tester online and tried to find the leak, but I think it was too breezy that day, couldn't see any smoke coming out anywhere. I opened the gas cap to make sure the smoke was getting back there. Do you know the best place to hook it into? I took off the hose that feeds the purge valve and used that. Other thing that maybe you know, is the vent valve open when the engine is off?

 

[TechGuru]

Probably not. I'm betting shops have to somehow manually actuate the valve...

 

[Drewmcg]

Pretty sure vent solenoid is open normally. This is required so that fuel vapor can vent to atmosphere as gasoline heats up in the tank on a warm day. It passes through the charcoal filters, which adsorb the gasoline vapors, before venting outside. Then, when you start the car, the PURGE solenoid periodically opens so that outside are can be drawn in (again, through the open vent solenoid) to draw those captured fuel vapors into the intake manifold to be burned by the engine.

The only time the vent solenoid is closed is periodically when the PCM decides it needs to test the EVAP system for leaks. At that point, it closes the vent solenoid and (I think) opens the purge solenoid for to draw a set vacuum. It then closes both solenoids and looks (using the fuel tank pressure sensor, I think) at the decay of the vacuum. If its not within spec by a little (your case) you get a "small leak" code. If its not w/in spec by a larger degree, you get a "large leak" error.

You should take your 'sploder to Eric O @ South Main Auto in Avoca, NY (my favore YouTube mechanic!). He'll take care of you and can certify that you pass the state requirements. Drew.