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1998 Volvo v70 XC AWD Horrid Gas Mileage


Drewhop

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The front o2 sensor has been replaced. I also had a ECT code and that was replaced as well.

 

The codes are reading p0131 Oxygen Sensor Low Voltage Bank 1 Sensor 1

The pending codes are p0172B Bank 1 System too rich.

 

Last week I found a vacuum leak and it seemed to clear up for about 2 hours. Car was running great. Car was boosting properly. Engine lights came back on and car had these codes again.

 

My major problem is the exhaust smells like fuel. Smells very rich and I am getting (dash measurement) and old school measurement of about 11 mpg. 16gallons of gas mixed city/hwy driving was around 180 miles. My last fill up on tank was slightly less at around 10.5 mpg.

 

The o2 was replaced before I purchased car. So it could be a bad o2 but it has less than 5k miles on it. And is obviously new. I have never seen a 02 sensor cause that drastic of a drop in fuel mileage which leads me to believe that it is not just an o2 causing my problems. I am also getting what sounds like a rattling from the blow off valve. I had a similar noise happen on my 1987 Toyota Supra turbo and replacing blow off valve cured it. (it is constant noise tho and not just when under boost)

Also this noise seemed to clear up after I found the vacuum leak last week. And it returned after check engine light had come back on.

 

The timing belt and pcv system was supposedly done about 5k miles ago as well. (All of which look brand new.

 

Here is what the data stream is reading

 

02 Sensor 1/1 0.00V

02 Sensor 1/2 0.48V

 

STFT Bank 1 Sensor 1 0.0%

STFT Bank 1 Sensor 2 -3.1%

Short Term FT Bank 1 0.0%

 

After doing some more reading around web. I am getting conflicting info. One place says sensor 1 should read 0.00 V but if sensor 2 is not reading the same then I have a clogged catalytic convertor. Any advice. I really need to get better gas mileage than a drag car.

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someone correct me if im wrong, but the pre cat 02 sensor should never read 0 volts unless its out of the exhaust stream. maybe you got a bad sensor, you should have a one year warranty on it, swap it out and see if that fixes the problem.

 

That is problem I am having. I cant find a legitimate answer to that.

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