I have 2000 Grand Prix 3.8 which keeps tripping a P0442 code only on the initial couple of km's of a trip. I erase the code and it does not re-appear till the car cools and proceed on another trip. I have replaced the gas cap with a quality cap, the canister vent solenoid and the purge solenoid in the engine compartment.I'd say if there was a leak the code would appear
on a constant basis just not on the initial cycle search.Stumped on this one. Bruce