Horrible Gas Mileage

[pagrey]

I personally wouldn't replace anything until I calculated mileage like @Viking Jeeper says, even the IAT.

 

[Steel City 06]

For the oxygen sensors, I found that 5-sided crowfoot wrenches made the job a lot easier. The wrench slides right over, and you have your choice of many angles to ratchet at.

 

[John Wolf]

How many gallons of fuel does it take to fill it up on "empty"? Even when mine goes well below E in the red, I've never put more than 17 gallons in it to fill up a 19 gal tank, and most times around 16 gals to fill. Wonky level/gauge system.

 

[pagrey]

Wonky level/gauge system.

It works kinda like this, especially the newer models

 

[TJ2]

Those special O2 sockets with the slot milled into them for the O2 wiring are used to install a new O2 sensor, not remove the old one. If your existing O2 sensor is typical it is seized in the header and that slot cut into the side of the O2 socket can cause the socket to spread open and slip/spin on the sensor when enough pressure to remove the sensor is applied.

To remove the O2 sensor use a standard 7/8 deep socket or, depending on which one it is, a box-end wrench. Cut the wires off from the old O2 sensor so the standard deep 7/8" socket will fit over it. And because O2 sensors are so often seized, it may be required to get the engine good and hot to help get it to unscrew. It's can be a painful bitch to work in that area when the engine is hot so be careful.

Thanks JB. As always, I will take your advise.
If only there is enough space for my two fat arms.

 

[John Wolf]

It works kinda like this, especially the newer models

View attachment 183590

Hahaha!! Yep, that's about how mine works, it's a 99. Wonder if it would hurt anything to run out totally one day, just to mark the display where true E is?

 

[RMETeeJay]

Also, i should of mentioned its the flex a lite electric fan with 2 stage aluminum radiator. (For best flow). Plus has an electric dial to set temp, which i believe is 195

I'm not familiar with these. Where is the temperature sensor for the fan located?

If you had it set to 195 (assuming that the coolant temperature was also at 195), that could explain your issue.

 

[JEEPCJTJ]

Those special O2 sockets with the slot milled into them for the O2 wiring are used to install a new O2 sensor, not remove the old one. If your existing O2 sensor is typical it is seized in the header and that slot cut into the side of the O2 socket can cause the socket to spread open and slip/spin on the sensor when enough pressure to remove the sensor is applied.

To remove the O2 sensor use a standard 7/8 deep socket or, depending on which one it is, a box-end wrench. Cut the wires off from the old O2 sensor so the standard deep 7/8" socket will fit over it. And because O2 sensors are so often seized, it may be required to get the engine good and hot to help get it to unscrew. It's can be a painful bitch to work in that area when the engine is hot so be careful.

The bolded part has got to be the best idea I've ever seen. I'm smacking myself for not coming up with that myself when doing both my TJ last month and my Ram last week. Luckily I didn't spread out my special O2 socket but none of them were an easy removal.

 

[pagrey]

Hahaha!! Yep, that's about how mine works, it's a 99. Wonder if it would hurt anything to run out totally one day, just to mark the display where true E is?

Nope, just carry a gas can. Every Jeep I've seen when the needle just leaves the white paint on the letter E to the left it is empty. So if you can see black between the E and the needle you are on fumes, totally out of gas.

 

[AndyG]

Those special O2 sockets with the slot milled into them for the O2 wiring are used to install a new O2 sensor, not remove the old one. If your existing O2 sensor is typical it is seized in the header and that slot cut into the side of the O2 socket can cause the socket to spread open and slip/spin on the sensor when enough pressure to remove the sensor is applied.

To remove the O2 sensor use a standard 7/8 deep socket or, depending on which one it is, a box-end wrench. Cut the wires off from the old O2 sensor so the standard deep 7/8" socket will fit over it. And because O2 sensors are so often seized, it may be required to get the engine good and hot to help get it to unscrew. It's can be a painful bitch to work in that area when the engine is hot so be careful.

Awesome post.

Those sockets can't be beat on a the NV3550 back up light switch on the transmission either.

 

[Cristophermm]

Well I'm late in the discussion. But, I have the same problem that DR7 had.
All good with the cats, new O2 sensors, oil change, new spark plugs and doing the same mileage 150-160. 8 mpg, and yes I did correctly. No codes in the pcm.
I have done everything that is in the topic. The only thing I didn't change yet is the IAT sensor.
Hope somedoby can help me

 

[RMETeeJay]

Well I'm late in the discussion. But, I have the same problem that DR7 had.
All good with the cats, new O2 sensors, oil change, new spark plugs and doing the same mileage 150-160. 8 mpg, and yes I did correctly. No codes in the pcm.
I have done everything that is in the topic. The only thing I didn't change yet is the IAT sensor.
Hope somedoby can help me

Welcome!

What method are you using to calculate? What is your tire size? Do you have a non-stock speedo gear installed? Does your exhaust smell rich after warmup?

If you complete your profile's vehicle details, it can be helpful when you ask questions of the group.

 

[Cristophermm]

Welcome!

What method are you using to calculate? What is your tire size? Do you have a non-stock speedo gear installed? Does your exhaust smell rich after warmup?

If you complete your profile's vehicle details, it can be helpful when you ask questions of the group.

I have this problem when I saw my tank go empty to easly. So, I filled the tank and take a look to the gas gauge. And it tooks 62 km (38 miles) to consume 1/4 of the tank, 124 km (77 miles) to consume 1/2 of the tank. And I did this three times (Three full tanks) until it was always empty.
First time I saw the consumption problem. So, I filled the tank. Did the calculation to see the MPG, it was 8 MPG.
Second time, they did the Tune-up. Nothing changes.
I go to another repair shop and they fixed some things that were barely wrong, but not the big deal. Everything was the same.
The third time I read here that can be the O2 sensors, so I changed the two of them. Nothing has change.
No codes, every test is good. So, I don't know what can be
Right now I have 1/2 tank and drove 124.6 kilometers (77.4 miles).

Sorry I thought I already fill the info about my Jeep. I just did. But here it is.
Wrangler SE 2004
2.4L
All stock, no mods.
Tire size 31.

 

[RMETeeJay]

You have larger than stock tires (the SE came with P215/75R15 which is 27-28" diameter) with the stock speedometer gear, which causes your trip meter to be off.

I'd recommend starting over with your calculation.

1. Gas up the tank to full (it's helpful to stop filling the same way each time so you can compare results. I stop at first click.) and reset the trip meter.
2. Drive until you're almost empty.
3. During gas up:
   1. Multiply your trip meter reading by 0.1185 (because your tires are ~11.85% larger diameter than stock)
      1. Add this value to the trip meter reading for your corrected kilometers driven.
   2. Take note of the exact liters required to fill tank.
   3. Divide the corrected kilometers driven by liters to full and report back your result.

You should be somewhere between 14.7 (city and 12.4 (highway) L/100km for the SE.

 

[rasband]

You have larger than stock tires (the SE came with P215/75R15 which is 27-28" diameter) with the stock speedometer gear, which causes your trip meter to be off.

I'd recommend starting over with your calculation.

1. Gas up the tank to full (it's helpful to stop filling the same way each time so you can compare results. I stop at first click.) and reset the trip meter.
2. Drive until you're almost empty.
3. During gas up:
   1. Multiply your trip meter reading by 0.1185 (because your tires are ~11.85% larger diameter than stock)
      1. Add this value to the trip meter reading for your corrected kilometers driven.
   2. Take note of the exact liters required to fill tank.
   3. Divide the corrected kilometers driven by liters to full and report back your result.

You should be somewhere between 14.7 (city and 12.4 (highway) L/100km for the SE.

Then fix the speedo gear issue and never need to think about this again (unless you change gearing/tire sizes).