I made a number of mods recommended here and it looks like my fuel consumption is worse than it used to be before the mods.

Looking for some guidance on what I should do and where I should looks to try to improve this.

• Installed the bored out TB form 'theXJfiles' - works fine.
• Installed a Spectre CAI - works fine.
• Installed new 703 injectors - reset the computer twice - works fine.
• Installed Magnaflow exhaust - works fine.
• Installed mandrel bent 2.5 exhaust pipe - works fine.
• Installed 0 and 2 AWG power cables and better ground - no issues there.

going uphill, computer shows about 7-8Mpg
going on flat road, somewhere about 17-18-19 mpg

My Suburban burns less gas. I can also see that I need to fill the Jeep quite often - more than one would expect...

Used to be somewhat better before the mods. Howsoever, car does not feel like it is running rough and shifting is smooth. If anything it feels like it has way more power and wants to jump...

Is there a way to reprogram the ECU at the dealer, to account for the new diff gear ratio (4.10) and larger wheels (32s)? Maybe that could improve fuel consumption as well...?

Anything else I should look at?

Thanks.

 

Is it possible that its running really rich? I have seen a few people do the MAP sensor mod to get their jeep to run a little leaner since they upgraded the injectors and throttle body... maybe im just crazy

 

I would hand calculate fuel consumption instead of using the overhead. Also take into consideration your driving pattern...are you now giving it more throttle cause it sounds cool and has more power? I would also recommend a programmer that allows for adjustment of gear ratio and tire size

 

When I redid my exhaust, I dropped from 18mpg to 15mpg. Blew my mind; tried to diagnois everything. resetting the ECU netted 16.5mpg. Until I realized that I totally kick it from a stop bc it sounds amazing. I now drive like a grandma and get 18-19mpg consistently.

 

Do you know your odometer is off? Just throwing this out there... My xj has 31s but for every 3 miles I go I actually go 4? And you may think that's not much but that's the difference between 16 mpg and 10 mpg. For example 300/20 = 15 400/20 = 20. Makes sense?

Edit:
And make sure your doing (miles driven from last fill up) / (amount of gas pumped in)

Otherwise your findings will be off each time.

 

Actually, this is great observation - the overhead indicator might be off by the same amount the speedometer is.

I will do a dummy check - fill the tank, record the mileage traveled (with offset) and see where it really is.

I can definitely feel like the tank needle drops faster than it used ot.

Does anybody know if there is any merit in bringing it to the dealer to adjust ECU parameters, like wheel size and axlew ratio? Can they at all do that?

I do it on my Chevy with a Superchips unit and it changes the way it drives, shifts, gets better mileage, adjusts the speedometer to wheel size, etc.

 

I'll be curious what you find here.

I have a newly remanufactured ATK longblock in my '98 Sport, along with a 2" lift, Surco rack, and 235/75-15s. New plugs, wires, cap rotor, cooling system, neon 4-hole injectors, cat and muffler, O2 sensors, and a reset computer, stock intake, intake, air cleaner, TB, exhaust manifold and downpipe. After about 8000 miles of break-in and the motor not being so tight, I was getting about 13.7 with an even mix of city/highway in my daily work commutes, and about 17.8 on highway only.

Someone mentioned in a thread about cheap O2 sensors and problems they can cause. While I had no obvious troubles or CEL, I did have the cheap O2 sensors. I switch them out to Bosch units. My mixed use went up to 14.8 and my all-highway went up as well. This past weekend I loaded up me, the fiance, and our 140 pound Mastiff in the XJ. I also hooked up my 5'X10' foot single-axle trailer and about 250 pounds worth of stuff on it and took it to our family land; about a 110 mile round trip. Set the cruise at 65 and had the air going full blast in 97 degree heat. I got 18.2 MPG on that trip. Towing a trailer! Glad I got the Bosch units!

I am curious if there are any options for reprogramming the computer on anything pre-99 to get even better mileage.

 

I lost about 1.5mpg since I've added the following mods on XJ. Winch Bumper, Winch, Rock Sliders, Gas Tank skid, Steel Wheels.........

 

I've got the fix for all MPG related issues....

























































Drive a Honda it's a Jeep boys fuel economy was definately not in consideration during production

 

No thanks, I rather not have to worry about my DD getting stolen by all the local latino's

I'll stick to my DD/ Auto-X'r that gets 32mpg

 

703 injectors don't increase mpg

 

Forgot about these - added all of them and also rear bumper, tire carrier, roof rack, a bunch of lights and a second battery...

 

Sold my 90 supercharged NA a year ago. Had 60K on it and I was the second owner. All FatCat Motorsports suspension etc.

 

Crawl back under your rock slimeball spammer.

 

Nice. Mine did have m45 supercharger but I sold it to a buddy when I was going To sell the Na. Once I am done with the Jeep I plan on building a 2nd engine an turbo kit . Right now I have a jr header magna flow hi flow cat and catback. Fm coil overs and sway bars. An the hard dog hardcore m2 double diagonal rollbar.