Gas mileage issue

[Shallowrunner]

Hey guys, need your thinking hat on to tell me what I am missing here. I am currently average 15.6 mpg on an 85 toyota 4runner 2.4L automatic with BF's 31.5s.

Things I have done:
*rebuilt engine (long block)
*cleaned out intake
*triple checked timing
*replaced all fuel injectors (had fuel leaking into the oil pan)
*replaced TPS sensor
*Readjusted the valves
*Replaced O2 sensor
*replace cat and muffler
*Cleaned cold start injector
*new plugs
*new wires, cap and rotor
*replaced timing switch sensor
*replace factory air intake with aftermarket spectra

And I have replace many other items as part of the rebuild. Most of the time the truck just seems a bit sluggish. Only one have I gotten 17.4 mpg. I checked the mileage every fill up. I got the 17.4 after I replaced all the injectors so I thought this was the fix, but the very next fill up lead to 15.2 mpg. I am out of ideas as what it could be. Some thoughts I have been giving are pressure regulator or fuel pump. But seems like to me the ecu would regulate how much fuel is going into the system based on feedback from the 02 sensor.

I always leave it in overdrive and only turn it off when I come to a long incline. My cylinder pressure is 165,170,172,168.

I looked up fuel mileage on this vehicle and automatics are suppose to get 18 in city and 20 on the highway. I would assume this is with factory tires.

Is 15.6 right based on my vehicle descriptions? I got 17.4 at one point so I am thinking I should be getting at least 18 on the highway.

Any thoughts are most appreciated on this guys... my gas mileage SUX....

Thanks.
Shallowrunner

 

[the_dingman]

Depending on how you drive (city/highway), that sounds about right. Having the automatic transmission and larger tires will make your economy go down compared to others. I have a 5 speed with 30" BFGs and I do about 19-21.

 

[SV_Dude]

You should be getting better than that. I just rebuilt my motor with pretty much all new stuff that has a wire attached to it. I have 4-5 inches of lift with 35" tires and stock gearing. I'm getting about 18-18.5 mpg's. I drive my runner like an old man and mostly on flat roads.

 

[the_dingman]

You should be getting better than that. I just rebuilt my motor with pretty much all new stuff that has a wire attached to it. I have 4-5 inches of lift with 35" tires and stock gearing. I'm getting about 18-18.5 mpg's. I drive my runner like an old man and mostly on flat roads.

I imagine that with 35s, you've probably changed your gears, which would help offset the loss by having larger tires. Having a freshly rebuilt motor, and driving like an old man on flat roads will help.

 

[SV_Dude]

I still have stock 4.10 gears right now. I haven't installed my 4.88's yet. I'm hoping I'll be at 20mpg or so when I install my 4.88's. :boink:

 

[thatoneguy]

Check your timing. For me, it had an enormous effect on my mileage.

 

[Shallowrunner]

What can be the issue?

So any ideas where I should start looking next to bump up that mileage? I did not replace every sensor. I know that a lot of people often say this, " Somedays it just runs great and other days it just feels sluggish". I know this does not say much but this is pretty much the exact description of what happens.

Here is a bit of info that maybe of value:

When it is running great.... I usually press down on the accelerator pedal about 1/2 inch to get plenty of get up and go power and if I go beyond this... the vehicled down shifts and accelerates nicely.

When it is running okay or not as good I am pushing down almost 2 inches.... and no dropdown in gear , no great acceleration... and the engine (air intake) just seems to bog down. I would say an example of this is like try to take off from a dead stop in second gear. Do you all think this could be a faulty TPS sensor?

I just at a loss......

Shallowrunner

 

[SV_Dude]

It's hard to say. When you tell us that sometimes the transmission will down shift and sometimes it doesn't, it tells me that it could be a transmission issue.

I would dig through the FSM and see what it has to say in regards to auto transmissions and read through the troubleshooting section. It may describe your shifting issue and could solve your problem.

 

[Shallowrunner]

Tranny

Hmmm..... Hadn't considered the tranny to be the issue. I'll take a look tonight and see what checks I can perform on it. Thanks for the suggestion. I will also check the timing again as someone suggested.

If any other ideas... Let me know please. They are most appreciated. I just hate to think my old ford f150 v8 gets better gas mileage than my favorite 4runner.

Shallowrunner