ccooper1234

OK I'm getting crappy gas milage and was wondering if the o2 sensors were the cause. At idle both the sensors read 1.0v but when driving they fluctuate from 0.1v-0.9v but the mostly stay at 0.7v. Are those reading OK or should they be replaced?

IslandXJ

Your upstream should read steady but the downstream should be jumping all over the place. The upstream o2 sensor is the only one that will affect your performance. The downstream is for emissions.

Bustedback

WRONG. The upstream should vary up and down, the downstream sensor monitors the catalytic converter performance and should stay pretty steady. Both sensors are for emissions, as is the MAP, TPS, VSS, CTS, IAT, and EVAP system.

IslandXJ

I got the 2 mixed up. But I don't think the downstream sensor will affect your performance or mileage.

ccooper1234

Which one is which?

Bustedback

Upstream is before the cat.

ccooper1234

Man its a pain trying to get the o2 sensors out when you don't have that size wrench.

Jeepxj1234

If you're for sure replacing them, I cut the wires coming out and used a deep socket and breaker bar and pb blaster to get them out. Just make sure to cut the wire between the plug and the sensor (so you can still pull the old plug out and install the new sensor like normal).

ccooper1234

Is there a certain way I need to install them?

Jeepxj1234

Have you looked at them? They just unscrew and unplug. Oh but you need to reset the computer I think which requires connecting the negative cable to the positive terminal for 10 seconds or something like that. Google it.

ccooper1234

Everything is done already.