EVAP Leak (Troubleshooting)

Ski-Free said:

The CEL only comes on after the ECU runs two EVAP systems test and they fail. For it to run them there are specific conditions that need to be met that are usually favourbale to highway driving so that’s why you’re seeing the CEL only come on when on the freeway..........

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I did not know that, thanks you.

Jnsfox said:

Mine had the intermittent gas smell also. Had to change the fuel tank vent valve to get rid of the smell on my forester, it's on top of the gas tank, was accessible from the back under the carpet.

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I'll check that out when I do my searching around for leaks back there. My timing belt project got put on hold mid way through, so digging around for leaks got pushed back as well.

So check this out. We went on a 4,000+ mile drive over Christmas 2018 and New Years. Before we left I took some sil-glyde and smeared a thin film of it on the gasket of the gas cap. Guess what, no more evap codes! It requires the cap to be tightened really well, like three good turns, not revolutions, just three good turns that make the cap click. For those of you that can't seem to find the very small leak, it may just be the gas cap gasket needs some lube on it to allow a better seal at the filler neck. The only time the codes came back was when my wife filled it up while I was inside buying something. After that I made sure to turn a few more times and in a month's time, the p0442 and p0457 have stayed away. Prior to the sil-glyde even tightening the cap really well would result in the p0442 coming back. So give the sil-glyde a try if you still get the codes and nothing else appears to be wrong with the other components.