New Oxygen Sensors 0n `99 Wow!

I just replaced the 2 forward oxygen sensors on my 99 suburban with the 5.7. The vehicle had 112,000 miles on it and the exhaust smelled
like it was running rich even after warm up. After 2 tankfulls my gas mileage went from averaging 10.5 mpg to 13.3 on tank 1 and 14.3 on tank 2 all in city driving and the exhaust began to smell normal. I have not had it out on a long trip yet to check the highway mileage. Used the Bosch oem replacement sensors bought at Autozone for about $58.00 each, the wiring harness was the identical plug in.

Hi, did your old ones trigger a light or was this just a good idea.My 94 has a very rich smell to it but no light!

Hi, did your old ones trigger a light or was this just a good idea.My 94 has a very rich smell to it but no light!

Hi...

No, I had no light on the dash just bad gas mileage and the exhaust smelled as if the truck was running rich even after warmup. I figured
I could replace both sensors for not much more than having the dealer
get the diagnostic codes.

Thanks again for some good info,my 94 has smelled very rich since purchase in jan.(but no service light)assumed it was characteristic of an oil burnin (doesn't smoke)192,000 mile motor.Nope oxygen sensor replaced,carbon monoxide smell gone,owner very pleased!!!KUDOS

Hi again
Your welcome. I am glad that it worked for you. That sensor should be good for another 192,000 miles!

Would you get a code if the O2 sensors were bad? What would the code read? Thanks Dave

Hi

I don't know if a bad O2 sensor would give you a code or not. I replaced mine based only on bad gas mileage and a rich smelling exhaust. Good luck.