Pontiac Repair: Auto repair, pontiac sunfire, 2001 pontiac sunfire

Question
My car (2001 Pontiac Sunfire) Has The check engine light on And when you are diving or at a stop sign the rpm gauge gose all the way up to a 4, and the acceloration takes forever to pick up. We had put on the computer a while back and it was the oxygen sensor. I was just wondering what do you think it would be? And what shoul I fix?
          We had told a person at Auto Zone what it did before when he put on the computer that gave a reading of the oxygen sensor, which we did not fix because of funds, and he told us to put some fuel injecter cleaner. Which we did,and the engine light went off but, the light came on about 2 weeks later. That's why I'm asking for your asstiance becuase that's the only car we got?.

Answer
there is a engine speed sensor somewhere on the engine.i would check this because it controls the rpm gauge.this also sends a signal to the computer.if your oxygen sensor is bad it will cause your engine to run poorly and get bad gas milage.you will be money ahead to replace this.these new cars are all about sensors to keep them running good and getting good gas milage.the bad part about it is the price to replace them.