First of all I just wanted to say hey to everyone. This seems like a really nice place.

Now I have a 2000 ssei. The problem is the engine will buck sometimes. like when I am driving it will just automatically give itself more gas and the rpms will raise. Also if I am just sitting idling it will just die out. I am getting a code for a fuel lean bank 1. The engine just idles very eratic, dies out sometimes, and just accelerates for no reason at all sometimes.

Things I've already done:

oxygen sensors
cleaned the MAF
new fuel pump
checked for vaccum leaks

THANKS IN ADVANCE

Welcome to this tight-knit family Coojo. Now, one option would be to dump the car and get another one but I'm sure others will yell at me for saying that. Maybe the computer is tricked into thinking that the car is not getting enough fuel or too much fuel and adjusted those things. Maybe the computer is on its way out. I'm sure others who are much more experienced will come help ya. Again welcome, you'll like this, I know, I did.

ya I kinda thought that too. but after all the money ive already put into it I really wanta be sure this time.

I'm going to guess the catalytic converter is bad. This should be moved to the 2000-2005 Mech. and Maint. forum so the Gearheads can give you a speedier reply.

The rear oxygen sensor has no effect on the car'* performance.
I'd be looking at fuel injectors at this point, or checking for further vacuum leaks or a cracked upper intake manifold. I'm assuming you've checked fuel pressure?

Where do you live?

I'll move this to the proper section for you.

Maybe the cruise control is fritzing? (for the sudden acceleration, I mean) Does the gas pedal move at all when it accelerates?

well i did check the fuel pressure and it was reading a little low which is why I put a new fuel pump on the car. some things did improve but not the inital problem. I live in chicago by the way. I will have to check the injectors. Is there a way to check the intake manifold?

BTW even while I have the gas pedal pressed at times the power will just cut out and then kick back in violently.

Crankshaft sensor? or injector.

Except for the acceleration, it sounds similar to when my oxygen sensor was flaking out. What brand sensor did you put in? The consensus is nothing but AC-Delco. Others have had bad experiences with Bosch, and I went through 2 Borg-Warner'* in a year. If you didn't put in the AC-Delco, you may want to give that a try.