2000 Chevrolet Cavalier

Engine Performance problem
2000 Chevy Cavalier 6 cyl Two Wheel Drive Automatic 110000 miles

Lately, when I am driving and my foot is on the gas pedal, suddenly the engine seems to hesitate briefly and the speedometer needle drops -- say from 60 to 40 -- for a fraction of a second. The driving speed certainly does not decrease by anything like that. This does not occur when my foot is off the gas pedal.

I brought the car to an expert in fuel injection. He hooked up his computerized sensor and found nothing wrong.

What could the problem be?
May 16, 2010.

I brought the car to a transmission shop. As soon as I described the problem, the proprietor said that I had a faulty speed sensor and sent me to a speedometer place. The speedometer man removed the sensor and tested it. It tested OK. Then he put back the same sensor and we went for a spin. The problem has disappeared -- at least for now.

Any explanations?

May 20, 2010.
Speedometer man took out the speed sensor and tested it. It tested OK. He put it back in place and the problem disappeared. It returned after 3 weeks. The transmission man told me to go back to the speedometer man and have him replace the sensor. Speedometer man said I should have the transmission drained and refilled. The transmission man refused (said that either the transmission is OK or it needs to be rebuilt), pulled the sensor and found it clean. He put in a used sensor (and ordered a new one), and the problem seems to be solved.

Jun 21, 2010.