9.5 mpg on my FJ80, any ideas to improve it? (1 Viewer)

[enriquelaija]

HI, I believe this is the first time posting here, I have a 97 FJ80 with Diff Locks and I love the car, but my mpg is really low, the CEL was ON due to the P0401 and I added a resistor to fool the computer and it worked, after that I had the CEL ON again and this time was due to the O2 sensors, I have replace them with new ones and the CEL is off again, I was expecting to see an increase on my MPG, but nothing, still the same, should I fix the EGR system expecting to see MPG increase?
I am in Tijuana and we do have every year the environmental tests, but not as critical as CA
Thanks

 

[Irish Reiver]

That kind of equates to what I get when running back and forth to work. Lots of traffic lights etc.

 

[decoco]

un burro wei, no gasta gasolina...

dude, it's an 80, while you're a little low, if you're stuck in traffic, this is along the low sides of normal.

if you haven't done a tune-up: distributor cap, wires, plugs, rotor- this may help - to the tune of 1 mpg. Nothing is going to turn the badest ass civilian full size suv designed in the late 80s to 26 MPG.
Also what size of tires?

 

[livelarg]

The only way I've found that improves my mileage is to get another set of keys....keys that fit a smaller car!

I'm kidding, but the reality remains. It's a big heavy suv. It takes a certain amount of energy to move it around. There really isn't a way to get more energy out of a gallon of gas.
And not really any way to make the engine move that big rig with using less energy.

One tip though 30-35 percent of mileage is killed from acceleration from stops.
The more smooth you leave a stop, the less fuel it takes. Makes a BIG difference in town

Good luck!

 

[greentruck]

I use the truck for running errands around town most tank fills. I'm lucky to see 10 mpg, usually less here in winter (not so much a problem in Tijuana)

I also have a P401 that pops up from time to time. I kill it off with the ScanGauge

Pump your tires up to a higher PSI is all I could recommend. You're probably doing as good as possible. But...Welcome! Hang with us here and maybe you'll find something that can help.

 

[Heckraiser]

Get out of the city! I just went on a trip to the mountains to hang out with the family and my gas mileage mysteriously increased by 3mpg

 

[Brentbba]

It would help letting us know one question that's been asked - tire size. If you've gone larger than stock, your MPG will be off approx 5% as I recall. Any other mods like front/rear bumpers, roof rack, etc that would add weight or wind resistance to the truck? I get 10 at best around town correcting for running 285's.

 

[sbman]

HI, I believe this is the first time posting here, I have a 97 FJ80 with Diff Locks and I love the car, but my mpg is really low, the CEL was ON due to the P0401 and I added a resistor to fool the computer and it worked, after that I had the CEL ON again and this time was due to the O2 sensors, I have replace them with new ones and the CEL is off again, I was expecting to see an increase on my MPG, but nothing, still the same, should I fix the EGR system expecting to see MPG increase?
I am in Tijuana and we do have every year the environmental tests, but not as critical as CA
Thanks

A big part of it is the stop and go. I drive in Tijuana fairly regularly and mexico in general and there is a lot more stop and go there even when there is no traffic. Stop signs at literally every corner.

If you didn't reset your ECU after replacing your O2 sensor, try that, just disconnect the battery for a few minutes. The EGR is supposed to increase mileage as well because it recycles waste heat back into the engine. I usually get 10+ around town and 15+ on freeway trips. My O2 sensor quit working a week ago and the CEL came on. Now the computer is in open loop mode and I'm getting 8, I've got new O2 on order.

 

[bugsnbikes]

o2s are good for quite a few mpg hit. if properly tuned engine- o2 sensors working well- u should get 14-15city 18-19 hwy with sub 33" tires and relatively stock weight. firming up the lockup on torque converter- dialing in shift points/ kickdown cable/ slightly bumping up timing/ synthetic lube in axles/ gutting cats/ fan clutch / new water pump and bearings........lots of pm / things can be done to get you back to stock mpg ratings. imho.

 

[CRSHR]

EGR (exhaust gas recirculation) is actually intended to lower combustion temperatures in order to reduce NOx emissions. Because exhaust gas can not be burned again(no oxygen) it will lower combustion temps. In training we were told only a couple hundred degrees but supposedly does the trick. As far as fuel milage goes I can't imagine it making a noticeable difference. But there are a lot of factors that can play into it as well such as driving conditions, ambient temperature and quality of fuel.

 

[enriquelaija]

My tires are: LT285/75R16, have a roof basket and a winch, besides that, not sure what else is causing this low MPG, I do know that the MPG on these beautiful cars is low, but I think that I am the lowest of the lower, I would fill comfortable being able to achieve 12 or 13 MPG, but not really sure how

 

[AlaskanLX450]

Big tires, added weight and added wind resistance in a vehicle that was engineered when fuel prices and economy were not the forefront of anyones conversation....

As mentioned before, drive like there is an egg between your foot and the accelerator pedal and it will steadily increase the MPG, otherwise get used to fillups every 175-200 miles! My mileage (and highway performance) increased a touch without the roof basket, the wind resistance is pretty noticeable!

Otherwise, 10ish MPG is right in the ballpark of a healthy 80

 

[mrsleeve]

Like others have said, stop and go city traffic is your biggest issue even if its not heavy traffic to try and bob and weave though but just having to stop and go for traffic control. I get about 10.5-11.2 MPG in city stop and go, but with lights every mile or 1/2 mile or so, On the highway I see about 14-16 depending on elevations, wind direction, how heavy my foot is on the trip, length of run between stops or slow downs, and I am correcting my distance for 255/80/17 (true 33" tires)

 

[NorthStar96]

Check for a leaking fuel line or tank.

 

[enriquelaija]

Check for a leaking fuel line or tank.

I guess that this is the only thing missing here, I have not been able to locate the hole in the gas tank

 

[greentruck]

Haven't had the problem, but most here report the tank usually has a leak in the top around where there's a dimple in it for the e-brake assembly to clear. That means it tends to leak when full, I suppose. You won't be able to see the leaking area without dropping the tank, although you should see where it dribbles down the outside. If you did have a gas leak, you can usually smell it. So if nothing visible and no gas odor, it's probably not a leak.

 

[enriquelaija]

So, as I've previously mentioned, I tricked the ECU by adding a resistor on the temp sensor to avoid the EGR code P0401, should I go back and really fix this issue? Would I see a better MPG if the EGR system really works as it is specified instead of being tricked on my car by the resistor?

 

[BILT4ME]

There are (3) possibilities:

1) Install an inverter to convert from 12 VDC to 120 VAC.
Buy at least TWO box fans.
Mount the box fans on the rear bumper, making sure the airflow is blowing AWAY from the rear of the truck.
Plug in both fans and set to "HIGH" before you leave. Measure your mileage.

2) Install a 10 ft tall pole on the rear bumper/hitch.
Place another horizontal bar slightly above the roof line that swivels on the first pole.
Sew together a few heavy canvas sheets in a triangle shape.
Secure the triangle to the poles
Drive WITH the wind, and adjust the "SAIL" to improve the mileage.

3) Put the truck in neutral and shut it off when driving downhill.

 

[enriquelaija]

Ha, that is funny, please do not take me wrong, I am willing to pay the MPG that my FJ80 is giving me, I just wanted to make sure that these levels are "normal".
On the other hand let me tell you that I have installed a HHO system and I was gaining 20%, but I have removed the system since it was getting clogged too often on the hydrogen generator cells and I have decided to remove it because it was not worth it the effort to keep cleaning the cells. I had a switch installed in my dashboard to turn the system on and off.

When it was "on" I was getting with 20 liters 60 miles instead of 50 miles (Hence 20% gain) , I was carefully measuring this by adding only 20 liters at a time, it is kind of tricky to measure your MPG since it is also affected if you are uphill or downhill even if you think that you are in a flat surface.

If the car is a little bit uphill it may turn off your gas light, but if is a little bit downhill turns your gas light on, so I had to be very careful on reading the odometer while measuring my MPG.

Anyway, just my 2 cents......