2005 Deville evap control leak

[procharlie]

I am helping a lady with a 2005 Deville that has error code P0455 EVAP emission control leak. I am looking for a diagram of that system so I can look for a loose hose, etc. The gas cap is not the problem; it had already been replaced as the dash still shows a "check gas cap" display after a new cap was installed, and I know it is on tight. She also has error codes P0300 (multiple misfires), and P0420 (catalyst efficiency low), but first I want to fix the EEC leak and see if the P0300 code goes away. Any help is appreciated. 

 

 

[rockfangd]

Welcome to CaddyInfo.

Check the filler tube where the gas cap seats. They get rusty there.

Check the filler tube itself. In the wheelwell. They rot there, especially where the bracket is welded.

Check for obvious unhooked or broken hose under hood to the purge valve. There will be a green capped test port somewhere atop the engine. Maybe firewall side.

As for the misfires, If this is a 4.6l v8 my first bet would be the coil pack unit on whichever bank is showing misfires.

It is one unit that does all 4 cylinders on each bank. 

[procharlie]

I found a leak, it was some holes in a plastic pipe running from the fuel tank to the emission module under the car. Looks like someone working under the car hit it with a sharp tool - file/saw/etc? - of some kind and put a couple holes in it. I sealed up the holes and hope that solves the problem. Haven't heard back from her, so assume it helped. I will check to see if her misfires are still there, and check the coil pack if necessary.

Thanks for the help.