I'd recheck your install of the spark plugs too. If they are not tightened in all the way you can get slight misfire an unburned fuel. With the engine idling you can try to push the plug wires onto the plugs a little tighter and if one of the wires gives you a pulsating feeling the plug is not in right. You should feel nothing.

At a dealership I worked at I saw that more than once from someone that had never changed plugs before, and one guy totally ruined a head by misthreading a plug into the aluminum and then tightening the hell out of it.


Rule number one: If you do some work on your car and a new problem immediately pops up, recheck whatever it was you just did. It happens to everybody.

How can I tell if the O2 sensor is going bad?

Pull it and take a look to see see how much crap is on it is one way. If there is a way to test with a meter, someone else will have to post. An O2 for something that old would be so cheap I would probably just swap it out. I have read from a local auto writer that you can clean the sensor with a wire brush and sometimes extend the life of one that is coated with soot, but I have never done that myself.

Keep in mind an O2 sensor only varies your fuel delivery UP TO 10%. If you feel your milage is wayyyyy off, the O2 sensor might be part of the problem but not all of it.


Even if you don't drive agressively what is you cruising speed? Guys on the Subaru board are convinced that the Legacy will deliver decent milage cruising up to about 72-73 mph, but going higher than that they claim drops milage significantly on long trips. Your cruising speed can have some effect if you are driving 80 mph.

I have a '96 4-cylinder camry as well. It gets 31mpg going 80mph on the freeway. I would definitely check the tire pressures.

Might do a compression/leak down check on it, too.

My '02 Camry gets 34mpg on highways.