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Decreased Gas Mileage

Moriarty581

NAXJA Forum User
Location
Maine
I have a slightly modified 89 XJ 5 spd and had been getting 18 to 19 mpg. then overnight i experianced decreased gas mileage and EGR valve failure. On a long trip. I plugged the EGR and replaced the MAP Sensor and O2 Sensor, but the gas mileage did not increase. Could my O2 sensor have burned out due to not having the ERG Valve in place? I have been told that this could happen. Also it dosent seem to have the power that it used to. I put Bocsh Plugs an wires in about 3 months ago and checked the rotor it looked fine. so bacicly i am at a loss as to why the old girl is sucking gas and loseing power.
 
I found out that the stock Plugs are the best thing for the engine or Champion plugs, and yes by plugging the EGR valve the o2 sensor will burn out and cause you computer to malfunction and get worse fuel milage...
 
XTrmXJ said:
I found out that the stock Plugs are the best thing for the engine or Champion plugs, and yes by plugging the EGR valve the o2 sensor will burn out and cause you computer to malfunction and get worse fuel milage...
would the O2 sensor burn out quickly? like within 200 miles? and as far as the plugs go they worked fine previously so i dont think that is the problem with the power. would the malfuntioning O2 sensor affect the power? also for referance i droped about 3 to 4 mpg. Thanks for the tip on champion plugs though..
 
Sorry about that, let me correct myself, It wont burn the O2 sensor up but what will happen is the signal will not get read properly so the engine wont function properly giving you bad fuel milage... Put EGR sensor back in and things will work properly...
 
XTrmXJ said:
Sorry about that, let me correct myself, It wont burn the O2 sensor up but what will happen is the signal will not get read properly so the engine wont function properly giving you bad fuel milage... Put EGR sensor back in and things will work properly...

I already replaced the EGR Valve with no change in power or gas mileage. So it looks like it must be something other then the O2 Sensor. So much for an easy fix
 
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