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running rich

Y

yourconfusedhaha

NAXJA Forum User
Location
vancouver
i have a 2000 cherokee, strait 6, running 31's,

i used to get around 15 mpg but latley it seemed to drop to around 9 and theres a good bit of suit build up in the exhoast pipe

it doesnt show any check engine lights and everything appears normal
anyone got any ideas of what it could be or i should look for?

thanks
 
well the mileage dropped because u put 31's on and probably stock gearing. i have 31's and 307 rear end gears and i get 12 at best mpg. Plus i have no cat just a cherry bomb side exhaust and intake. So get gears or make that engine breathe a little more
 
not always, depends on how it goes bad, if it's just not reading as good as it could, it won't set a code. If it's bad internally,(short,not reading at all) then it will set a code.
 
The O2 sensor has two parts; the heater circuit and the sensor...
Could be just the heater circuit has gone bad...
Problems caused by bad sensors dont always cause DTCs....
 
Have it checked with a scanner anyway, the CEL light may be bad.

O2 sensor, TPS and a clogged cat converter are the most likely causes. Could be all three. I would guess the front O2 sensor(s-?) is biased to the rich side, but pretending to be working, and the cat is still working marginally, or the CEL light is dead.
 
:roll::roll:

was it (old one) covered in soot? they will begin reading sloooooooow when they "soot up" and will cause the ecu to increase the pulse width to compensate for the slow signal response. This, in turn, causes more soot and slower response. That's the main reason to change them when the factory recomends.

:roll::roll:
 
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