Replace O2 Sensor?
Make 'em Last
03-24-2010, 10:14 AM
Background -
Replaced the EGR valve in in Jan '10 for my '99 Intrigue 3.8L NA 167K (did throw the appropriate code), and 6 weeks later experienced stalling (at idle & closed throttle at low speeds). Previously, because of the UIM design failure, had lost a lot of coolant through the exhaust (hydro-locked twice). Decided to replace the exhaust system (cat, resonator & muffler), but the problem turned out to be a bad EGR valve - ouch. Yeah, the one I replaced. So now everything seems to be ok. Checked gas mileage a couple of times on my daily commute (96 miles) and got about 24 MPG. That's what I've gotten before, as it's a combo of stop & go and Interstate.
Question -
So, should I replace the O2 sensor (pre-cat)? All I/M monitoring tests complete (according to my Innova 3100 OBD II scan tool), and I read 0.044 Volts from the sensor (according to my Cen_Tech CAN OBD II EOBD Scanner). I see Open Loop status when I first start the engine and when under a load / WOT. Rest of the time get Closed Loop status.
Can understand that the O2 sensor may degrade over time, but don't like changing parts without a reason. What do you folks think? Thanks in advance.
Replaced the EGR valve in in Jan '10 for my '99 Intrigue 3.8L NA 167K (did throw the appropriate code), and 6 weeks later experienced stalling (at idle & closed throttle at low speeds). Previously, because of the UIM design failure, had lost a lot of coolant through the exhaust (hydro-locked twice). Decided to replace the exhaust system (cat, resonator & muffler), but the problem turned out to be a bad EGR valve - ouch. Yeah, the one I replaced. So now everything seems to be ok. Checked gas mileage a couple of times on my daily commute (96 miles) and got about 24 MPG. That's what I've gotten before, as it's a combo of stop & go and Interstate.
Question -
So, should I replace the O2 sensor (pre-cat)? All I/M monitoring tests complete (according to my Innova 3100 OBD II scan tool), and I read 0.044 Volts from the sensor (according to my Cen_Tech CAN OBD II EOBD Scanner). I see Open Loop status when I first start the engine and when under a load / WOT. Rest of the time get Closed Loop status.
Can understand that the O2 sensor may degrade over time, but don't like changing parts without a reason. What do you folks think? Thanks in advance.
Airjer_
03-24-2010, 12:45 PM
Is the O2 switchin and/or is there a code for the O2 sensor?
Make 'em Last
03-24-2010, 12:49 PM
No, there is no O2 code (or any other code stored). Haven't seen any pending codes. Not sure what you mean by O2 switching.
Airjer_
03-24-2010, 02:27 PM
The O2 supplies a signal to the PCM based on the amount of oxygen in the exhaust. Less oxygen=more voltage. More oxygen=more voltage. The signal from the O2 will switch between the high and low voltages, as the engine is running, fairly rapidly. If the O2 is doing its job sufficiently there will be no codes or any reason to change it. If the sensor gets lazy (takes longer to switch between lean and rich voltages), stuck low, or stuck high and/or falls out of the expectations of the PCM than the PCM will flag a code letting you know there is a problem.
BNaylor
03-26-2010, 12:51 AM
You gas mileage is acceptable and I would not replace the 02 sensor unless there was a drastic change compared to your previous mileage figures.
Note: The front 02 sensor is only used in the closed loop mode of operation.
Note: The front 02 sensor is only used in the closed loop mode of operation.
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