Can O2 sensors start going bad without throwing an engine code? Would the front two sensors make the motor run poorly and the back two make the exhaust sound funny?

I was also thinking of changing the spark plugs sometime soon which might help.

 

The front O2 sensers might make it run funny. The rear ones only check the cats for emmisions. I bet it needs a good tuneup with new front O2 sensers

 

My last truck (a foreign model) had the O2 sensor going bad. Would run for a week or two, throw a code, reset and it would run for a week or two before throwing the code again. But when the sensor started to go bad, the MPG dropped -- a lot.

 

Ya and thats another thing I should mention my milage is right around 20 on the hwy and doesnt change.

 

I replaced my front two O2 sensors at 100k miles (123k currently) and had a dramatic increase in gas mileage.BTW,no codes were present.I think O2 sensors get "lazy" but will not throw a code.

 

Ya I looked at the front two sensors today, and they dont look easy to replace especially the one on the passenger side. A lift would be nice! If i get some ambition Ill get it done along with the spark plugs.

 

mine went in my truck.....they also seamed to get lazy.....then throw a code becaue i started to see a gradual drop in MPG then all of a sudden WHAM down to 8 mpg......i normally get 18 so that was a gradual drop to 14 then down to 8 then the codes came......good luck.....the heat makes them a real pain in the A$$ to get off sometimes.....

 

Ya i really think I want to change the front o2 sensors. Anyone have advice on doin this? The drivers side doesnt look to bad, but the passenger side looks like a PIA!!!!

 

I know this is and old thread but I wanted to Change mine out too
My truck is at 150000 and want to know where they are located.
any help would be good