low gas mileage

[kennyface]

i seem to be getting less and less for my gas lately....had a broken muffler and catalytic converter, replaced those....hopin my mpg would sky but that never happened....any clues tips???

 

[89xj]

O2 sensor

 

[cbremer]

O2 sensor

agreed... replaced my O2 sensor, started getting 2-3MPG more.

 

[SimpleXJ]

Yep, replaced mine and my MPG is back. If you wanna test yours - do it when the jeep cold. Unhook the O2 harness connector. With an ohmmeter take a reading off the two white wires on the O2 sensor harness. It should read between 5 and 7 ohms. If its out of spec its bad.

Another test is this: start engine and let it warm up to normal temp. Take a voltage reading off the O2 sensor signal wire and the battery ground. It should be rapidly bouncing between .4 and .6 volts. This must be done while the harness is still connected to the O2 sensor, and the vehicle running. If its out of spec, replace it.

SimpleXJ

 

[kennyface]

well i just replaced the o2 sensor which was way overdue....i dont think it had been replaced in over 50k. Am still getting about 11-12 mpg.This a combination of both city and highway driving

 

[NCSUcherokee]

you said you just replaced the o2 sesnor? was it the one up on the exhaust manifold? i was doing some work on my exhaust manifold last summer and somehow i knocked off a vaccum line. not sure which but it caused my milage to go down to about 8-10 MPG and there was a smoke comming from the exhaust (because it was running super rich)

 

[yuppiexj]

check the manifold gasket for leaks. My 94 got 13 mpg due to a blown exhaust manifold gasket. replaced that and it bumped up 4 mpg.
Remeber the o2 sensor only work properly if there are no leaks up stream from it.

 

[woody431]

Where is the O2 sensor located? I'll have to check mine to see if it's ok.

 

[Moriarty581]

Brake line Question

I have heard through the rumor mill that you can get 3 extra inches of slack in the rear brake line on a XJ by useing one from a YJ or TJ. Can anyone conferm?

 

[NCSUcherokee]

I have heard through the rumor mill that you can get 3 extra inches of slack in the rear brake line on a XJ by useing one from a YJ or TJ. Can anyone conferm?

what does that have to do with low gas milage?

 

[kennyface]

the o2 sensor is located before the catalytic converter. u shud see some wires run into the exhaust pipe. According to the manufacturer, its supposed to be replaced atleast every 36,000 miles.
Yea i noticed some oil on the bottom of oil pan but thought it was some dried up oil. I'm gonna check for leaks

 

[kennyface]

better mpg..thanks naxja

its taken a couple of 100's of miles but now seems to be working. am getting close to 15-17 miles a gallon on city driving which is awesome compared to the 8-10 i was getting a couple of weeks ago.
The oxygen sensor change seems to have done the trick. Am leaking some oil though, the leak is very slow though, i need some ideas for a quick fix to this problem.

 

[89xj]

where is the oil leak? hard to give advise not knowing where its leaking.

once you figure it out, do a search.

 

[DaveD in Canada]

Low gas mileage can also be a result of a cold engine. Have you checked the thermostat, making sure the engine is reaching normal running temperature?