Thanks for the reply tanprotege.

I would agree with you but not in this case. The car runs extremely well. Smooth through all gears, and through the revving cycle. I would think an obstruction would cause a lot of lost performance, while right now the car is getting amazing performance.

Now, I replaced the sensor tonight. I bought a Bosch Universal Oxygen Sensor from an OEM part dealer in town. It installed with no hassle. The one we took off the exhaust was not damaged or discolored or in any way different from a normally used oxygen sensor.

Right away I noticed an improvement with performance. Before the O2 sensor was replaced, I noticed the car would "load up" or run heavily. This did not effect performance of the engine, just made it seem like it was running rough. Before, I would back into my driveway (which is on a bit of an incline) and it would shake almost like a diesel engine. After replacing the sensor, it was very smooth. -- The reason why I could notice this improvement is from my older Protege. It doesn't run half as heavy as my newer Protege. Now, they run about the same.

I filled up the tank tonight, so I will update this post with results when the tank is almost empty. (this gives me a reason to drive the car a lot over the next few days )

Cheers,
Mike

 

Car is getting around 420kms(/9.36gal) on a full tank of gas, 27.7mpg. This is up from just under 260kms(/9.27gal) on a tank of gas, or 17.4mpg.

This is on par with my older, 2000 Protege.

Problem seemed to be the O2 sensor!