Bad air/fuel sensors?
 

Hi all! New to the forums and lovin all the info.

So, here's my issue...I have a 98 camry (calif emissions, 173,000 mostly freeway miles) and for the last year I have noticed that the fuel mileage has been getting progressively worse (down 6+ mpg). It has not thrown a cel, but I fear that one or more of the air/fuel sensors have gone bad, and possibly the cat. I have also noticed that the exhaust smells bad. The car still runs good, maybe slightly less power and a little rougher, but nothing extreme. The sensors and cat are the originals.

Since there is no cel, could it be that the sensors have not totally failed, but have just gotten lazy? Also, could it still throw a code w/o a cel? I'm wondering if I should take down to autozone for a scan. If I knew it was the sensors for sure I would just replace them, but I don't want to go and start throwing $ at the issue. On the other hand, I've been told that the sensors usually have a 100,000 life span.

OH, and my driving habits have not changed, been using synthetic oil for 4yrs, all mpg is hand calculated, fuel filter has 50k on it and air filter 15k. I understand that the oem fuel filter should last at least 60k, but that seems odd since most say to change after 30k or less. And, recently cleaned the TB.

Thanks in advance for your help!

Jason