I have a 2002 Monte Carlo SS 3800 series 2 with 254,000 miles give or take. Supposedly the engine has around 1000 or so. Anyways, I was getting a P0446 code. Evap system code. I changed the vent purge I think it’s called under the car beside the tank fillneck. Didn’t fix anything, I then changed the purge canister on the top of the engine, also didn’t do anything. To add, I can’t fill up at a gas station either, cuts off every few cents. Though just today, I was filling up with a gas can, got it to almost full, a quarter tank away and now the vehicle runs really rough, dies after about 30 seconds and will rev up at times. Then stalls like it’s flooding itself out. I have no idea what to do with it or what could be wrong.
I changed the vent purge
I then changed the purge canister
Well which one? I think you're a little confused. The vent valve and purge valve are separate things, both connected to a charcoal canister which serves them both.
Both the DTC P0446 , and your symptoms at the gas pump agree with each other, and would seem to indicate a problem with tank venting.
Command the vent solenoid open using a bidirectional diagnostic tool (or maybe you can manually apply ground or 12V to it) . 1st make sure it is responding. See if it's clear either by blowing or using compressed air. Command it closed and use a smoke machine to see if it has leaks. Check wiring harnesses and connectors for electrical faults.
