After being installed an o2 sensor and a thermostat on ...

What was the original reason of replacing the O2 sensor and t-stat?

Also, is the Check Engine Lamp comming on?

-Rip

Because of the temp gauge was registering cold when the car should be in operating temp, check engine lamp had come on. Upon hooking up the computer, it indicated that thermostat was stuck and also the o2 sensor was needed to be replaced. After the repair, temp gauge registered correctly in the middle like it should when the engine reached the operating temp, however, almost immediately the engine started to misfire and lost power (during test drive) and the check engine lamp came back on.

Edited by Customer (name blocked for privacy) on December 20 2006 at 9:23pm

It sounds like a bad oxygen sensor was installed, especially if it was an aftermarket part and not factory. Often, aftermarket oxygen sensors are inferrior or damaged from mishandling, and when installed can cause a variety of performance issues. Your mechanic should be able to easily test for this condition by viewing the oxygen sensor values on his scan tool. If the sensor he replaced is showing a biased reading, when in relation to the engine's actual condition (lean or rich) it will entail a defective oxygen sensor. Or, you can have the old one reinstalled, PCM (engine's computer) reset, and see if the problem allieivates. If the oxygen sensor is not at fault, then some wiring was disturbed when the repairs were made.

-Rip

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It makes sense. However, when the check engine lamp came back on after the repairs, he'd hooked
his scan tool back on. At this point, shouldn't the scan tool indicate an 02 sensor problem again to make him think that 02 sensor he changed could be a defective part?

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