re: 2002 Toyota Celica GTS with 1.8 VVTL-i engine and 6-speed manual trans ~98k miles. She’s a screamer (and my last ride was a 2005 G35 coupe. This car is much more fun.)
Runs great… a real screamer that just averaged 29.5 MPG over the last two tanks of fuel in mixed driving, including occasional traffic slow downs. That’s without trying.
So I get gas one day and just throw about 35 bucks worth of premium (required) fuel into her, and it gets the fuel level up to between 3/4 and Full. I tighten cap (yes, til it clicks) and fire up my little commuter go-kart. She stumbles. She bogs. I can’t make a leap and say she was stumbling from being rich, but she was stumbling, bogging and seemed to clear out after 60 seconds. After 60-90 secs, she’s back to normal. I write it off as maybe a loose cap on the last tank, or something. This is at a BP station, and not some off-shoot station. Been there many times with other vehicles.
Ok… so about half-way through that tank, the ‘check engine light’ (CEL) comes on. I tighten the fuel cap and go about my business. Bugger stays on for days and miles of various use. Got code checked: p0441
I replace the fuel cap, but p0441 is the ‘evaporative emissions’ code and can be various things for a mechanic to experiment with, some at great cost - some less than 100 U.S. bucks. CEL still on. Car runs fine, and this code should not affect performance, but it won’t pass inspection if it is on and I would like to be enviro-friendly and not have vapors escaping into the air.
So… time for fuel… and she’s running great. Same deal: 35 bucks worth and she’s between 3/4 and Full. I tighten the new cap, the CEL is on, she’s been running great… cranks, starts… stumble…press accel pedal and she tries to clear out… she stumbles at idle speed for 15-20 secs… I press accel and clear 'er out. I drive home, CEL on, new gas cap, still w/ p0441, she runs great.
If it has a charcoal canister to catch fuel vapors from the tank, it could be full of fuel. When you fuel up the pressure of the gas going in forces fuel back into the intake and it runs rough. Instead of inhaling vapors, it could be taking in raw fuel. But as you say, it could be a number of things. The coincidence of refueling is what suggests the canister plugging.
I’d say Al Bundy is on the right track. Likely some component of the evaporative emission control system is leaking, causing both the code and the symptom. The charcoal canister is a possibility, but not the only one. Loose or damaged hoses are sometimes found, and a common Toyota problem is a faulty VSV (canister vent solenoid). It’s going to take some testing to pinpoint the cause in this case.