my car has been burning alot of gas lately. For example, if i put 20 bucks i get roughly 100 miles before empty. its totally stock and i just did a tune up on it. I replaced the spark plugs/ wires/ fuel filter/ cap and rotor/air filter/oil change. I dont see any visible gas leaks and am suspecting a faulty o2 sensor. Now my question is would a faulty o2 sensor always produce a check engine light?

 

When I had a fualty O2 sensor my CEL wasnt on. Also check your tire pressure, most people overlook that.

 

anyone else?

 

nope, you can have a "going bad" o2 sensor, and get horrible mileage.

 

For the time it takes you to find out if it is your O2 sensor, you could have already spent around $80 for an NGK/NTK replacement. You would have paid the difference already with improved gas mileage!

 

did you check the old spark plugs to see if you running rich or lean? I would check that first to give you better idea of what's going on before you start assuming random parts.

 

just change the 02 sensor and see if thast was the problem

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1337whp &raquo;</TD></TR><TR><TD CLASS="quote">just change the 02 sensor and see if thast was the problem</TD></TR></TABLE>


Exactly. It's part of maintenance anyway. Wouldn't hurt to change it.


Now if he's had the original 02 sensor that came with the car, then it would really be a problem.

 

What year are you?? If it is obd 2 you can mill around at 3k and after about thirty seconds or so if the o2 by the cat is really close to being out of tolerance it should go off. It does on my friends car anyways. His is just about out of tolerance and if he stays at 3k it gives him a cel code for secondary o2. I don't know if this will work for you but its worth a shot. Or if you have a multi meter you can measuer the resistance of the o2 sensors and compare them. Some one has done that before. Their should be an article on what the resistance should be.