I have a 97 jeep xj on a 3 inch rc lift on 31 BFG k02 and I get very poor gas mileage (11.1 mpg) I have replaced fuel injectors with Bosch 4 hole injectors replaced entire ignition system ( plugs wires coil rotor distributor cap etc ) and I am trying to figure out why to do about this I only get about 180 miles per tank. Any advice will help thanks. And also I have 3.55 gear a/t and the 4.0

 

O2 sensors. I have a bad one in my WJ and with a new rebuilt engine, I'm only getting 11.7 myself. My scanner comes up with a P0152, Bank 2, sensor 1 shorted to voltage. Apparently we damaged it when we took the manifolds off.

Funny, I have a friend in RI by the name of Billy Stott!

 

I forgot to mention it also has 2 brand new o2 sensors in it

 

Could be a multitude of sensors out of spec. Hell could be bad grounds giving the computer bad information. Check your block and body grounds then break out the multimeter for sensor testing. Do you have an FSM somewhere? It gives test values for the various sensors that feed the computer information for fueling. TPS, Coolant Temp, O2, IAT, and MAP. I'm sure I'm missing a few in there. But with a multimeter and the FSM you can narrow it down to a sensor out of spec after making sure you have good grounds and a good voltage going to everything.

 

What brand? NTK came factory, and for some reason, other brands dont always perform as well as they could. Or should. I have come to realize this with anything dealing with how the engine runs in these things.

In addition to what downs posted, other factors are tire pressure, alignment, driving habits, engine condition, fuel pressure, etc..

 

Depending on the driving conditions 11 mpg isn't that bad, that's about what I got with 31s and a 3" lift.

 

I have a multi meter I’ll do some checking on some sensors as for driving habits don’t drive too crazy top speed I get is about 65 I’ve just seen lots of people getting a lot better gas mileage then what I get and would like some gains to save some money

 

I believe they were ntk paid 140$ from Napa for both of them

 

Before you get all Crazy, jack the Jeep up and make sure none of the brakes are grabbing, I would start there first.

 

3.55 gears and 31's are not a bad combo, so you probably could get a little better mileage.

Where did you get the 4 hole injectors?

Also, are you totally sure the ignition system is good, (i.e., all the connectors are properly seated, plugs gapped, etc. etc.) ?

What tire pressures are you running?

 

Heh. A lot of people might dismiss that, but it's a very real consideration. I just replaced the front calipers and rotors on my WJ, and picked up about 1.5 MPG. Not huge, but what if I pick up the same when I do the back? 2-3 MPG for doing basic maintenance? Not too shabby.

 

I have found that using it for frequent short trips could cause that

You dont mention driving habits or possible extra weight, bars etc

I average about 15mp/G (US), fill up ~220 miles, but that is when the light 1st comes on steady, so a somewhat subjective measure

travelling on the open roads, fully warmed, it will get 16mpg

mine has headers and 2.5" exhaust, 3" lift, 30" tyres, no additional weight

 

Yep. Big time. It's very hard on the engine and exhaust system.

 

This.

or carefully touch the calipers/drums after/during a long drive. See if they are consistent, none should be particularly warm after a long drive with minimal braking.

 

Back when I would drive across PA with the same setup in my '88 I could get 400 miles a tank no issue. I would make sure your sensors, throttle body, kickdown cable, air filter, etc are all in check. Sometimes it's the simple things that cause issues.