Cannister purge issue, surging
 

After I park my '98 Contour with Zetec 2.0 4 facing downhill, I get surging at all speeds, including idle where it's most noticeable. The engine will speed up maybe a few hundred rpm for about five seconds, then slow down for about the same amount of time, and repeat.


I'm thinking gravity might be pushing fuel through the lines and loading up the charcoal canister, then the on/off speedup is a purging process. This can't be entirely normal, so how do I fix it?

When you put fuel in the tank do you try to get as much in as you can ? If so , canister may be overloaded with fuel. Stop putting fuel in when the nozzle first shuts off if this is what is happening.