Again I've owned many trucks but this one is ridiculous....

Hey 1996sportxj what size injectors did you jump To? what size injectors come Stock? did you notice a power increase or a smoother Idle?

 

Injectors only really smooth out the idle. They do not increase fuel mileage

Just do like what is mentioned above. Major tune up then come back to us if there is no change

 

Im thinkin of runnin 31s also when I get a 4.5 inch lift. Did re-gearing it make much of a difference? I get about 13mpg now on stock tires and gearing. I was hopin it wouldn't change the mileage much with 31s.

 

If you're getting that with a stock XJ I think something is wrong. When mine was stock I was getting 18-21 mpg's. When I first went to 31's it ran bogged down and no power. I regeared and made a huge improvement.
If I could do it again I think I would have just done 3" lift with 30" tires. I've done too much to reverse it now.

 

Impossible to speculate exactly what mileage you're getting without a speedo. I know you think it's bad, but without data, you don't know how bad.

I agree with others that a full tuneup, new upstream oxygen sensor, test your map sensor, check for any codes, the basics.

Then see where you are at.

 

I just did the typical neon injector swap that is extremely common with the XJ. But once again, that isn't going to help mileage. I really like what they did though, better throttle response and smoother idle. Well worth the money in my opinion. I don't know how the size compares to that of stock. But when you talk of physical size, the neons are much smaller haha

 

For what it's worth, if the OP doesn't look elsewhere about the fuel injector swap, the reported increase in mileage afterwards is usually because the stock ones were either dirty or defective.

 

Very true! So if you look at one of my earlier posts, I mentioned using Seafoam, which would solve this problem

 

Ommmg but thats soooo much reeeadiiiinnnnggg. And yes a good dump of the ol' Seafoam should clean those up nicely

 

I dont know why I get such bad mileage, I drive normally and I've done a full tune up. The only thing I can think of is the o2 sensor. It passed emissions, so it cant be that.

 

that's where I'm at full tune up's been done, I haven't changed out the o2 sensors or checked the map sensor but I'll do that this weekend. As far as the injectors, I'm not a complete noob I know they won't increase MPG unless mine were dirty or fouled up but I asked more about the performance part.

Ill check all those sensors and ill try to replace the speedo sensor so I can get an actual figure for you...but I'm guessing around 13mpg.

 

Oh I forgot Seafoam is awesome....I've owned 2 toyotas, 1 iroc, 1 blazer and the jeep and I've used Seafoam on all of them ;-)

 

I've always been hesitant about sea foam because I don't want to free up gunk and block stuff in the engine, especially with an engine that has 250,000 miles on it.

 

I've never had any issues....

 

You'd rather leave all that gunk in the engine? I've never heard of anyone having problems with Seafoam when using it PROPERLY. The way I see it, the worst that could happen when using it properly is it could unclog build-up around a seal, causing an oil leak. But that would just be a great indication that that seal was bad anyway and was needing replacing