Code P0455 and the Gas Cap

[guruerror]

Originally Posted by guruerror

Now I'm getting P0455 and P0496 High Purge Flow...blah blah. I guess it's time for the smoke test.

I've also notice on my last three gas-ups that immediately after putting gas in the tank (whether it was a complete fill-up or not) when I turn the key the engine cranks really fast and starts to start, but then putters out (like it's not getting any gas). When I turn the key a second time, it gets a little better and almost idles, then putters out. On the third try it usually starts after a few cranks but idles rough for a bit, then it's fine and doesn't act up again until I put more gas in.

WTF?

I'm thinking maybe the purge valve up front needs replaced...$40 (GM 12581282).

I was poking around on a Cadillac forum where the same code and symptoms were discussed: "The first time it happened was after stopping to refuel after being on the road for about 4 hours. The car wouldn't start, even after letting it sit for a bit. Finally, I pressed the gas peddle all the way down and it fired up (acted like it was flooded)."

The Cadillac tech reported that this was a "condition that we used to refer to as 'flow during non-purge'. Basically the engine is sucking fuel vapors from the canister into the engine which will severely enrich it. If the computer doesn't know this is happening the fuel mixture won't be right and it will not run well."

Replacing the valve seemed to resolve the issue for the Caddy guys...guess I'll give it a try this weekend.