1999 Passat (V6) Hard to start after gassing up!
 

My 1999 V6 Passat's Check Engine Light started coming on a few weeks ago. Everytime we gas up the car, it is icredibly hard to start and keep running for a few minutes. Once the car finishes its' little fit before we ever leave the pump, the thing runs great until the next stop for gas with no other hard starts, hot or cold.

When I began I had 5 codes, 2 of which were cleared by replacing the engine coolant temperature sensor. While replacing the temperature sensor I also sprang for a new fuel cap and fuel filter whichI installed at the same time thinking one or both might be the answer to the rest of my problems. Following themaintenance, I cleared all codes and drove another tank of gas thru the car with the same hard to start problem at the pump.

Currently I have the following codes. (Description are per the Haynes manual)

P0455 = Evaporative emission control system, large leak detected.
P1136 = Fuel trim too rich at idle (bank 1)
P1138 = Fuel trim too rich at idle (bank 2)

I've been driving around with my code reader, checking regularly and have found that the P0455 is the first code to come in and hangs around for a while before P1136 and P1138 show up. Everything I've read points to a vacuum leak or a charcoal canister problem, or maybepurge valve problems. I don't have muchknowledge when it comes to the EVAP system and I'm looking for a little help. Any tips on how to troubleshoot to locate the problem would be great or maybe I should be looking at something else. Symptoms are still the same, car runs great except for immediately following a re-fuel.

Thanks,
Justin