Rough Running when I put fuel in?

[003KWK]

This is a weird one, in my 99 VT Ecotec V6.

When I go to the fuel station and fill the fuel up, when i turn the car on, it sorta starts up and idles really rough for like 3-5 seconds then comes good again?

I've also noticed too lately If I start the car in the morning and put my foot down and take off it will almost die as I accelerate then like 2 seconds later it stopps running rough and all's good to go for the rest of the day.

Maybe these two things are related, not sure, but would like to be able to work this one out.

[kart_racer]

With the petrol station thing, my 98 VT does the same thing, both with the auto and manual tunes I've had. It's just the PCM adjusting to the new fuel I think.

And I get the other one too! I'm thinking I need new o2 sensors.

[003KWK]

Yeah, haha. Whenever I have someone in my car, after it happens they go

" O_o wtf? "

It's just annoying and looks lame when you're putting away and everyone is probably thinking "haha what a ****box!"

[666vt]

mine does it too man, runs a bit rough on a full tank, and when nearly empty.

[pablo]

Well I fill my tank full till I see fuel at the top of the filler, and it ALWAYS runs sweet as a nut after, never any problem.
I wonder if some of the fuel is being sucked in to the manifold through the purge system? When you blokes have the problem, check the exhaust to see if the engine is running a bit on the rich side, (bit of black smoke outa the exhaust)

Pablo

[kart_racer]

It's not like it lasts long, maybe 10 secs of the revs dropping and coming back up a few times. It's just like what happens if you change the air intake and the PCM adjusts for the new air flow. I think it's just an issue with the PCM being a little slow to adjust to the new fuel.