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Old 08-21-2005, 04:33 PM   #1
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Default just double checking (o2 sensor)

Ok. I have finally had enough. My gas mileage + gas prices = unhappy logan.

When ever I say anything on here about my 14 MPG, everyone instantly says you need to change your O2. It isn't that I don't believe you, but it could be a number of things, right? I don't want to spend $50+ on a part, and not see a noticable change in my gas mileage.

So here is the litney of questions.

Say I were to pull a spark plug right now. It should have fouling on it, right? A bad o2 will make my car run rich (which kills MPG) and it will foul the spark plug. Bad logic, or am I correct.

Is my gas mileage THAT bad? I live about 7 or 8 miles from town, so many of my trips are going to be about 16 miles of HWY driving, and probably 2 or 3 or city driving. Bad part, I live about 2 miles from my work, so between 3 and 6 times a week I go 2 miles there and 2 miles back. I was talking to my cousin who has a 95 SE, and he lives 2.5 miles from work (he drives it even more often than me because he goes home for lunch) and he claims to get at least 18.

What do you think?
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Old 08-22-2005, 10:29 AM   #2
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when i was getting bad fuel economy i had my o2 sensor checked by my mechanic who has a good scan tool, and it sure enough was the problem. is there anyone near u with a good scan tool? that would be the easiest way to check it out, and for ur year shouldnt it only be like 28-35 dollars? or is 95 the year they went more expensive? i know mine is like 65 for my grand prix, and that is just one.:(
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Old 08-22-2005, 10:37 AM   #3
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when i was getting bad fuel economy i had my o2 sensor checked by my mechanic who has a good scan tool, and it sure enough was the problem. is there anyone near u with a good scan tool? that would be the easiest way to check it out, and for ur year shouldnt it only be like 28-35 dollars? or is 95 the year they went more expensive? i know mine is like 65 for my grand prix, and that is just one.:(
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Old 08-22-2005, 10:51 AM   #4
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You could allways unscrew the sensor (if you can get it out) and look at the tip.
Properly functioning sensors are chalky grey at the tip. If its charcoal colored its running rich and needs to be changed.
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Old 08-22-2005, 11:37 AM   #5
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Umm if you are just check to see if the computer code it might not with a bad sensor my car wasn't coding the o2 was bad I was getting 8mpg when I got her. YOur o2 could just be lazy which would mean it was in the proper diagnostic range for the car. It still doesn't hurt to check
SSEBONNE4EVA is right the tip was diffently charcoal color
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Old 08-22-2005, 11:42 AM   #6
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I got 26 after chnged but alsochanged the plugs on it and now get 26-29 mpg after I fixed vacum leaks.
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Old 08-22-2005, 12:19 PM   #7
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Default Re: just double checking (o2 sensor)

Quote:
Originally Posted by Logan
Ok. I have finally had enough. My gas mileage + gas prices = unhappy logan.

When ever I say anything on here about my 14 MPG, everyone instantly says you need to change your O2. It isn't that I don't believe you, but it could be a number of things, right? I don't want to spend $50+ on a part, and not see a noticable change in my gas mileage.

So here is the litney of questions.

Say I were to pull a spark plug right now. It should have fouling on it, right? A bad o2 will make my car run rich (which kills MPG) and it will foul the spark plug. Bad logic, or am I correct.

Is my gas mileage THAT bad? I live about 7 or 8 miles from town, so many of my trips are going to be about 16 miles of HWY driving, and probably 2 or 3 or city driving. Bad part, I live about 2 miles from my work, so between 3 and 6 times a week I go 2 miles there and 2 miles back. I was talking to my cousin who has a 95 SE, and he lives 2.5 miles from work (he drives it even more often than me because he goes home for lunch) and he claims to get at least 18.

What do you think?
Let me explain several things here...

You have the first year with a 4 wire heated O2, The NA'd 93 models uased a 3 wire heated O2....

The O2 sensor on your car is a heated design, in that it has a little heater in it that will help get the sensor to operating temps fairly quickly, this way the PCM can try to keep the air fuel ratio 14.7 to 1...

On the older single wire cars the O2 was solely heated with the exahust, so in the first few miles of cold start it would take a little bit for the sensor to read...

The newer designs have more to do with emissions, but every little bit helps in the way of fuel economy and emissions... As far as emissions go, both your 94 and my 95 meet teir 1 standards...

Frequent cold starts and driving 2 miles and then starting it again and driving 2 miles will use more fuel... But......

On my 95 with the same exact sensor you have, I have done as bad as 13mpg.... The sensor was almost dead... But the plugs did not come out fouled... I went from 13 city to 18 cty after the O2 replacement, thats allowing the PCM to relearn after I reset it... After that I managed 32 mpg on the road...

I also think I may be due for a new O2, and am going back to the TR55 plugs as well... I noticed as I was scantooling the car, the O2 was getting lazy.... I stopped to realize that its been 3 years on this O2... My worst milage on my trip was 27, the best was 30.... I have never done worse than 29 on the road... I am doing 18 cty at current tho... I was doing about 20 last year...

I can't say that this will be the cure to your fuel economy issues, but it may help... I'll assume that you don't drive it as hard as I drive mine tho...

Also the engine management system is diffren on the 94-95 as opposed to the 93-92-91-90 and so on....

The engine could still be cold, but after a couple minutes of driving, at the right speed, the PCM will apply the TCC even if the engine is like 130F... On a 91 if the engine temp is below 150F the TCC will not apply no matter what the speed... In the 95 if the speed is right, the TCC will apply... Say at 41-45 or 55-60 with a cool engine... The 94-95 models are a strange breed for sure...

If you replace the O2, try and stick with AC Delco, and you may want to replace the plugs at the same time...

Good Luck

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Old 08-22-2005, 12:36 PM   #8
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any one the ACDelco P/N for 2002 bville? N/A

is it AFS109 or AFS123??
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Old 08-22-2005, 12:47 PM   #9
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Quote:
Originally Posted by itsnitro
any one the ACDelco P/N for 2002 bville? N/A

is it AFS109 or AFS123??
I searched it and the one you want is AFS109 GM Part # 25312203

This is for an NA'd 3800 K engine...

The AFS109 is the sensor that is in the rear exahust manifold, the AFS123 is the sensor after the Cat...

So you want the AFS109

Good Luck

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Old 08-22-2005, 03:02 PM   #10
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Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by itsnitro
any one the ACDelco P/N for 2002 bville? N/A

is it AFS109 or AFS123??
I searched it and the one you want is AFS109 GM Part # 25312203

This is for an NA'd 3800 K engine...

The AFS109 is the sensor that is in the rear exahust manifold, the AFS123 is the sensor after the Cat...

So you want the AFS109

Good Luck
thannks!!! any 1 have a techinfo for it?? never done 1 be4
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