# O2 sensor Question



## Radco (Mar 6, 2009)

Hello . and thanks in advance, How can you tell if a O2 sensor is going bad?No Codes pop up... could a decrease in MPG be a sign? I am assuming that I may have a issue..I just picked up a 2000 Chevy/Suzuki 4x4 Tracker 2.0 motor 42000 miles on the clock.. I live rural.. No stop lights and very few stop signs,, We have 10% Ethanol in the Gas.. Use the 4 wheel feature a few times,, got 21 MPG.. Est 30 mpg hwy.. and I know est can be off LOL..Just changes the AF,, 20$ man that gave me a stroke .. Does this look average??? and can you use a universal O2 sensor with the same results? I see a BIG difference in $$$$.... Thanks Rich


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## kenmac (Feb 26, 2009)

It should give a code if the 02 sensor is bad


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## Rehabber (Dec 29, 2005)

Many things can affect gas mileage. First check the thermostat and make sure it is opening at the correct temperature. (if it is opening at a lower temp, the computer thinks it needs to enrich the fuel mixture) Maybe a good tune up? New plugs, plug wires, fuel filter, pcv valve, etc. and don't forget to clean the throttle body and mass airflow sensor. O2 sensors rarely fail before 50,000 miles. (and I don't recommend universal fit sensors, use an exact fit.)


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## Radco (Mar 6, 2009)

*Thanks*

Thanks for the help.. I did find a gasket leak at the flange connection on the exhaust.. I will do plugs this week, Change the gear oil (ALL) and motor oil to Synthetic,,, AF was dirty,, new one in,, almost had a stroke when I cashed in 20$ WOW they went up LOL...I also have a K&N Now for next change,,, Gas filter will be changed as well... Trasmission fluid will be soon..A older lady had it so I am assuming maint not on her to do list as pri 1.. Tire press was 40 PSI.. Road like a Buck Board LOL.. 30 PSI like a new truck,,  I will change all hoses and Rad fluid B4 Winter.....and maybe the plug wires,, STill cannt find the Cabin AF yet,, I know where it is supposed to be,, BUT no luck yet LOL. Got another Radio player,, The stock had a Cassette deck,, found one on E Bay w/CD off a 03 30$ Shipped,,,With VIN # as well..Plus receipt, to show its legal if I need unlock codes, I didnt ,,.. ANY other tips? For a cheap SUV this thing is GREAT,,,,,,Thanks again,Rich


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## Clutchcargo (Mar 31, 2007)

Your mileage sounds about right. You'll get better mileage when the weather warms up.


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## kenmac (Feb 26, 2009)

Radco, I have a 2000 mazda. It had a clogged passage to the EGR. At the time of the clog, I was getting steady 32-33 MPG. I cleaned the throttle body ( the clog) Re-set the ECM. Now I only get 27-28 mpg..Go figure


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## Radco (Mar 6, 2009)

*Thanks*

The Guy I got the Tracker from,,Private dealer, installed the Nex exhaust gasket, and did the breaks and rotars,, NO CHARGE! Seem alot smoother ... But between 1500/2000 RPM I get a light exhaust noise,, hit 2 k rpm quiet again,, I call him today,, to check it out,, But I did have him cleam the Throttle body as well.. The Tracker idless @ 750 rpm,,, and with EFI cannt adjust it higer...
Ken I hear you about fixing a problem abd getting less mpg lol.. Had that happen on my Intriped...
again everyone, thanks for your advice
Rich


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## Chemist1961 (Dec 13, 2008)

Just had 1 of 3 sensors done on my Lexus RX300 @155,000 miles. it was wonkey and fuel system cleaner, etc didn't help. Mileage was dropping and we could smell gas. Low idle was rough, check engine and ETC lights were on. We reset the system after reading the meter and it came back on a few days later.
Tech told me it sends a signal back to the ECU to increase fuel ratio hence the poor mileage. We watched the meter when he installed the new sensor and the ECU decreased the fuel ratio before our eyes from over 50% to back around 6% as he predicted it should.


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## Radco (Mar 6, 2009)

*Hey*

Sensor checks out OK... Exhaust leak fixed,, with new AF Im got 3MPG Better... Going to change the plugs.(43000 on them) and change the Front,Rear and Transfer case to Full Synthetic,,, and Full synthetic in the oil as well....I will also change the Gas filter..and cut it in 1/2 to see what 43k looks like wit our crappy gas ...Rich
Has anyone tries that New Hydrogen  gas that Shell sells? notice anything good or bad???


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## 2long4u (Dec 29, 2008)

kenmac said:


> Radco, I have a 2000 mazda. It had a clogged passage to the EGR. At the time of the clog, I was getting steady 32-33 MPG. I cleaned the throttle body ( the clog) Re-set the ECM. Now I only get 27-28 mpg..Go figure


An EGR pumps inert gasses into the intake. It only does this at part throttle. One of the side effects is a lack of power. You don't notice it because of the driving conditions. When you loose power it takes more to go the same speed, resulting in poor mileage. The EGR is used ONLY to reduce oxides of nitrogen.


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## Radco (Mar 6, 2009)

*Thanks*



2long4u said:


> An EGR pumps inert gasses into the intake. It only does this at part throttle. One of the side effects is a lack of power. You don't notice it because of the driving conditions. When you loose power it takes more to go the same speed, resulting in poor mileage. The EGR is used ONLY to reduce oxides of nitrogen.


 Thanks nice explaination


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