How do you know if your O2 sensors are going bad, I mean not shot where they are throwing a code or anything but when they are on there way out. I just got really ****t gas milage driving ont he highway up to NH and I figured it was because I put my flowmaster on backwards but before that I got 20MPG driving city. I have half a tank of gas to go through still and aftr that I'll tell you what I got.

 

Well, I never got a CEL light but my gas mileage was horrible...it dropped from 17-18 city to 12-13 city. I knew it wasn't maintenance related and there weren't any other problems so I decided to change out the O2 sensors. I changed them out with Bosch O2 sensors and gas mileage went back to normal.

 

ok I think that mine are bad so I'm going to see how much they are and replace them at some point

 

Your sig shows that your truck has 140,000 miles....have they ever been replaced before? If they haven't, they need to be.

 

I have no clue LOL, got the truck at 90,000 and havn't replaced them yet so I'm guessing it is. but I did get 20 MPG on one tank of gas. So 400 miles out of one tank and thats city driving.

 

When does the 02 sensor need to be checked around what mileage because usually when the light comes on its too late LOL and I just did a full tune up 2 weeks ago and only got 176 miles out of 16 gallons and 40 bucks so needless to say I am bit concerned

 

Ima say dirty Mass Air Flow Sensor....

 

How would some one with non mechanical skills go about checking this ?????

 

Their is only one sensor right? And when replacing the sensor do you need to disconect the battery?

 

It depends on your truck, mine has 2 but it's a 1994. I think the newer ones may have 3? But you will have at least 2, and yes, just for saftey's sake disconnect the battery.

 

Damn that means i have to buy 3 o2 sensor at 40 bucks a pop. That blows.

 

They have 2 before the catalytic converters and 2 after the catalytic converters for a total of 4. Depends on the year of the truck. I know from 2002 and on they all have 4 O2 sensors. The 2 before the CATs monitor air/fuel ratio and effect gas mileage (So if you are getting bad gas mileage without a check engine light and decide to change O2 sensors, those are the ones to change). The ones after the CATs just monitor the catalytic converter efficiency and have no impact on fuel efficiency.

They say they have a life of 100,000 miles. Mine lasted 4.5 years of every day stop and go traffic and a lot of idling.

I replaced mine w/ the battery disconnected (negative battery cable). As far as removing them and putting new ones in there, I changed them through the fenders (turned wheels all the way to 1 side and squeezed my arm/hand in there w/ a wrench lol). The passenger side on my 3.0 was easy. The driver side was a lot harder because everything was in the way.

You may want to clean your mass air flow sensor, especially if your running an oil wetted gauze type filter (K&N). Pick up a can of CRC MAFS cleaner or electrical contact cleaner and a security torx T-20 (I believe) bit. Unplug the wires, take it out of the housing (make sure it isn't hot), spray it a few times (not really up close with a lot of pressure, you don't want to damage the wires), let it dry for a couple of minutes, put it back in, tighten it down, connect the plug and there ya go, clean MAFS.

 

Thanx, im going to try that. ive been getting real bad gas mileage so hopefully this will help.

 

Thanks. What size wrench is needed to remove and replace the O2 sensors?

 

They have special wrenches just for 02 sensors you can borrow at Autozone

 

Ok thanks.

 

Last question maybe

This is the right one? 2003 Mazda B3000 O2 Sensor
Or either post me a part number please