Need help. SES just came on.

[Steve74-02]

yesterday I drive the car and all is fine. Stop at Home Depot for 30 mins. Starts fine, then before I even get out of the parking lot it starts to run real rough. I let it idle a bit and it seems better, then the Service Engine Soon light comes on. First it stayed on, then it was flashing, then it went back to steady on. The car feels sluggish now. I started it up again today and the SES stays on. I just let it idle, didn't drive it. Also seems to be running rich, but it was cold out so I'm not sure. 02 Z28, LS1, 6spd.
Any ideas?
I guess I should go get the codes read. Does Autozone do this free? There's one right by me.

[2manycis]

If you know it's running rich for sure, then I'd say look for a stuck open injector.

If you don't know the code though, have it read and make decisions from there. Things will be a lot easier. If it does end up that you're running rich, grab a stethoscope while you're at autozone for like $20 or so and listen to all your injectors for ticking. If one's not ticking then it's stuck/clogged and will probably need to be replaced. Might take you 10 mins.

[Steve Crowe]

Yes, by all means get the codes pulled including, if you can, any codes still stored in the history. There are a number of things that can cause this.