1998 Nissan Altima Bad MPG/O2 Sensors

MRKNC

MEMBER
1998 NISSAN ALTIMA
2.4L
4 CYL
FWD
AUTOMATIC
176,000 MILES

My MPG went bad about a year ago, after replacing plugs, wire, cap and rotor which was needed nothing changed. I got a live scanner from OBDlink and after changing the valve cover gasket everything seemed back to normal, for about 1/4 tank filling back up that 1/4 it seemed to go bad again (same gas station). So I started looking back at the O2 sensors checking out the charting on Torque I noticed that the sensor 2 seemed way bad, question is can you confirm with the charts I will attach.
Thank you very much
Michael

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3 Replies

RACEFAN966

MECHANIC
5,029 POSTS

The sensor seem a bit lazy but that it. I would get a can of sea foam and put it in your next tank of gas. Today's fuel isn't as good as it use to be and the ethanol and other chemicals are harder on our older vehicles. It leaves deposits on the injectors and in the intake and so on. I had to take the upper intake off my truck and decarbonize it to get my MPG back I was down to 8mpg. So what I am saying the sensor might help but using the sea foam to clean the fuel system and injectors should make an improvement. I do need to ask is the check engine light on? Thanks

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Thursday, June 5th, 2014 AT 7:57 AM

MRKNC

MEMBER
2 POSTS

No Check engine light, Should I still use the sea foam if I been using Lucas gas treatment and do wait till I need a full fill up?

Thank you!
Michael

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Thursday, June 5th, 2014 AT 9:44 AM

RACEFAN966

MECHANIC
5,029 POSTS

Yes try seafoam lucas makes good products but their fuel additive is to lubricate injectors not clean them. So use lucas about twice a yr. Let me know if it improves also if I remember correctly this car has a mass air flow sensor, get a can of mass air flow cleaner and clean it if it gets dirty it will make mpg go down too. Let me know how that goes ok.

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Saturday, June 7th, 2014 AT 6:45 AM