What are the effects of a bad o2 sensor?

[crazyfingers]

does it effect power and fuel economy in anyway?
i have a 94 v6 xle

[Curry]

I've heard a bad sensor can affect your fuel economy. Not sure about power.

[ghettosled]

a check engine light will appear, fuel economy will go down, power will probably decrease as well, engine might not run as smooth...

[bigbird]

^x2. the car will be running in "limp" mode and will screw with the timing and fule trim. eventually that will screw up your cat converter and ull end up with lots more to fix then just an o2 sensor.

[ECale3]

The O2 sensor will affect fuel economy and performance.

[toysrvmanager]

Remember the o2 sensor measures the amount of oxygen in the exhuast to determine how to adjust the air fuel mixture going into the engine. A fualty sensor can trigger the engine to lean out, which causes problems. It can also make it run more rich. This can also damage not only the cat but if left unchecked for an extended amount of time the unburnt fuel will wash down the cylinder walls and wipe out the block.

[Durrby]

Originally Posted by ghettosled

a check engine light will appear

I don't think it does. Before I replaced mine I was getting about 175-180 miles per tank. After I replaced it I could get over 300. That was the only sign it was bad, crappy mileage.

[Hajoca]

The CEL will appear only if the O2 sensor itself fails (like not heating to operating temperature on time, response time after ignition timing or fuel volume was adjusted by ecu, strong voltage signal, etc) but in your case it is not responding quickly enough to adjust fuel trim, but still not enough to throw a code. The cat was working properly to not trigger the after cat sensor too!

The lean condition usually usually gets noticed easier with knocking.

Some older O2 sensors (especially 1 wire type) would respond with very bad gas milage and not show fault code, and run in open loop mode.

[crazyfingers]

well i have both of those signs, i have terrible mileage plus the check engine light is on
and my HP is pretty crappy

but i only found out when i took it to get a diagnostics test
btw is there anyway to get those done cheaper than at the mechanic?

i dont wanna spend 70-80 dollars just to find out whats wrong with my car

[Hajoca]

Many chain auto parts stores will read the code and reset it free.

I bought a cheap code reader with cancel feature ($40 CDN).

[crazyfingers]

alright thanks, i wanna do another diagnostics test cause with the amount of time that passed from the last time i did a test i think another o2 sensor went out, the mechanic himself was saying the other ones were about to go out and i've recently experienced an even more decrease in power and fuel economy and i just got a tune up

[JalenWu]

Originally Posted by Durrby

I don't think it does. Before I replaced mine I was getting about 175-180 miles per tank. After I replaced it I could get over 300. That was the only sign it was bad, crappy mileage.

x2, same thing happened...bad gas mileage, then after replacing, kept thinking the gas gauge was broke b/c it didn't go down! No check engine light on my g/f's 93 camry (4cyl).