I need some opinions, I have a stock 98 XJ 4.o, 4 x 4, with 88000 miles, with all tune up's complete. Is 12.5 mpg city close to normal or do I possibly have something causing the poor mpg? Thanks
shaner

 

Definitly got a problem somewhere in there. Check all your CVC fittings. Something is wrong somewhere on this puppy. What all did you change and did you notice any increase in MPG versus before tune up till now. you should be getting close to 18.

 

I have changed plugs, wires,air filter,oil filter,tire pressure checked, greased all visible fittings,and had an injector flush. I noticed a slight change but then seemed to go back to its original mpg. I have suspected something wrong.I still need to change the fuel filter, I plan on doing that today or tomorrow.
Where are the locations of those CVC fittings...I know of the one on the valve cover.Thanks

 

Yes it is.

 

Check your O2 sensors too. I was getting about 12mpg for a week after my XJ threw an O2 sensor code. I just got into the ECM and deleted the codes, and I popped back up to 22 mpg.

 

In the city?

 

I had the computer checked three weeks ago at an Advance auto and the guy said there were no error codes that showed up.I asked the guy if he could delete any codes , he told me he couldn't do that, that it had to be done somewhere else....

 

To clear the codes disconnect both the positive and negative cables from the battery. Touch positive and negative cables together, you'll probably see a small spark. This will cause a capacitor in the PCM to discharge wiping the error codes from the memory.

 

Yeah, I get between 20 and 22 no matter where I drive.

 

I have been getting a good 18 in my 87 waggie and I don't have highways. Although I can't really call Radcliff a big city.

 

Yeah, I don't have highways either, unless I go to the next town over to buy a gallon of milk or watch a movie, cuz you can't do either in my town.

 

Well no one is forcing you to live in such a small town. But this is a mileage thread so you should tell everyone you have a four banger and not a 4.0L I6 so they won't all think they can acheive 22MPG.

I have a lifted (3.5") 4.0L I6 and it is an older Renix era Jeep and I get around 17.5-18 MPG combined driving. Not as good as a four banger but pretty decent. And I don't trust my speedo to give me correct figures so I rely on my GPS so I know those figures are pretty accurate. I would expect a little higher numbers on a trip.

 

I have the same problem,, I need to replace the O2 sensor , I will be happy with 17 MPG... im getting about 13.8 MPG right now...

 

It says so in my sig, and my little drop down thingy. But in case you missed it, I HAVE A 4 CYLINDER, hence my 20-22 mpg. The point of that post however, wasn't what mileage I get, but rather that the O2 sensor caused a drop of 10 mpg.

 

That and the inconvience stores in your town don't carry milk. LOL