For the last couple months my truck has been making a weird noise, like pressure building up and releasing coming from the gas tank. If I catch it while it's doing it and open the gas cap it'll quit for a couple minutes, so you can tell it has pressure building up inside the fuel tank. Just a few days ago it started to misfire (or I think), but just when I've been pulling and going up hills and stuff like that, so I'm having my local shop put in plugs and wires in a couple days. It finally tripped the CEL and i figured it would be a misfire code, but it was P0442, a small leak in the EVAP system. I'm guessing its tied into the pressure building up until I pull off the gas cap. I've been searching around on here and I'm going to check the gas cap seals and stuff. What have people found out with this and how is it tied into it misfiring, if it is? Thanks.

 

Well here's the system -



It's usually #9 that gives out on yuh, but not always. You have to get it checked for leaks. They can smoke test it or you can go thru it yourself with guidance. A Haynes or Chilton's service manual would help you there.

 

Here is some more info for you. Using jbrew's pic you can follow along with this.

P0442 - EVAP Control System Leak Detected (Small Leak) The PCM monitors the complete EVAP control system for presence of a small fuel vapor leak.
Probable causes
After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications Small holes or cuts in fuel vapor hoses/tubes Canister vent solenoid stays partially open on closed command Damaged, cross-threaded or loosely installed fuel filler cap Loose fuel vapor hose/tube connections to EVAP system components EVAP system component seals leaking (EVAP canister purge valve, fuel tank pressure sensor, canister ventsolenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly)

Regards

Jean Marc Chartier

 

Good post ^^^^

Also, being in Minnisota, you might want to check your overflow line at the filler neck. Mine rusted out and had holes in it at one time.

Some more info -

DRIVEABILITY CONCERNS

The EVAP system does not effect the operation of the vehicle. It is possible that a disconnected vacuum pipe beneath the vehicle in the Fuel Tank area could cause an unmetered leak in the Inlet system and cause poor idling.

The only way in which a driver may decide that the EVAP system is not working is when there is no hiss of vacuum as the fuel cap is released after the engine has run.

 

So do you think this has anything to do with it misfiring, or do you think thats just a coincidence?

 

you may also want to check if your gas cap is tight or not. this could throw an evap small leak code. then again like you said its building pressure so look for the weakest parts that are in jbrews picture.

 

No, just a coincidence. Do you by chance have a misfire code. Has the CEL blinked and turned off at any time? If so, you have a code set and need to get it read again.