I'm getting 8.9 Mpg out of my 97 4.0 4x4 on 3in 31's still on stock gearing replaced the speedo gear. It's has the following mods

ARB style Snorkel with K&n filter
63nm TB
NGK O2 sensor 7 months old
Mustang 4 hole injectors

The last full tune up is almost a year ago And even then it was getting only 10 mpg all city i very rarely get on highway. I seafoam it every 2 months and fuel injector cleaner every fourth half a tank as i only can afford to get half tanks with my pay schedule.

 

Is the Cel on any codes ?

I am willing to bet that NGK O2 is getting a bad reading. When replacing sensors always get them from the dealer Jeeps tend to spit out aftermarket sensors.

 

There is a CEL code but its for my Efan it went out and i replaced it but the code keeps coming back no matter how many times i clear it.

 

What did you install when you did the tuneup? Air filter, spark plugs, distributor rotor& cap, wires? Which ones?

Ever cleaned the throttle body? Poor vacuum on the MAP sensor can cause bad economy, as can a number of other sensor problems such as CTS.

Code returning means there's still a problem. What's the actual code? 1997 is known for wiring issues.

NTK (NGK) is actually the OE sensor.

 

I replaced everything the last tune up. Yes i cleaned the TB every 3 months with seafoam. The vac line on the map sensor is clear. The CEL code is P1491 but like i said i replaced the efan and it works fine yet the code comes back i clear it and within a week it comes back.



thanks

 

Well then then last issue is the distance between the gas pedal and floor it can be adjusted by removing pressure from the pedal assembly and what rest on the seat

 

How are you calculating your mileage? If your e fan is working then why would it throw the code? Something must be wrong still (though I'm sure it isn't affecting this). When you say you replaced everything what is everything? I've had plenty of people say they replaced everything but when they list what they did there was still things they didn't do. Just trying to help troubleshoot. Did you gap your plugs correctly? What's your air pressure like? Any other issues?

 

I use the trip meter every time i get the half tank i rest it then i take the old receipt and calculate the average miles. Also just i installed a overhead console and will be getting real time eco and Mpg. I've replaced the following

Plugs
Wires
Cap
Rotor
O2
IAC
air filter
Oil filter
Oil

Yes the plugs are gapped correctly.I have no clue why the code keeps popping up. No other issue with it. By air pressure do you mean tire or compression?

 

I dunno if it helps you, but I was getting 10mpg city. Never went on the highway. Now I moved to college and 75% of my driving is highway and I get high 16s, or even very low 17s.

 

im getting about 9 a gallon...if u find out anything let me know

 

Any thoughts or could be's?

 

Whens the last time you changed your diff fluid, or flushed trans? It wont do much but old oil may create a little resistance in the system. And what is your gear ratio? You can get a build sheet from Chrysler by emailin them. Thatll give you your ratio

 

Lol this.....

Last kid complaining about his mpg's and seeing how he drove I gave him one recomendation......

Get a 4" long 2x4 and place under the peddle. Problem solved. Lol

He did not find it funny.... but I sure did!

 

Stock gearing 3.55 also both was changed 3 years ago.

 

I pretty much keep under 3k on the tac.