Alpine114

99 4Runner, 3.4V6 5spd, 4x4 K&N Filter, Amsoil OIL and Filter,.....It just seems on average to get around 14mpg. No other mods, but wondering what else i can do to get more miles/gallon....Spark Plugs, Fuel Filter????

dexter

check the o2 plugs and the sprak plugs

Roadtripr

Usually my milage drops a bit in winter due to the different fuel. But 14mpgs sounds very low. A few easy things to do or check is:
Tirepressure (if too low you really loose milage)
Drive slower (stay away from doing 85)
Drive w/o the leadfoot (accellerate slowly)
Remove roofrack (if you have s Surco or Yakima)
Don't carry around a lot os stuff you don't need.
Maybe a fuel injector cleaning is needed.

theryanator

Alpine -

I have the exact same truck with the same problem and just calculated 12.6 miles to the gallon on my last fillup. I am tired of it and am taking it to my mechanic next week to look into it further than I can myself with my limited tools.

I have done the following:

Seafoam twice.
Redline SI-1 fuel injector cleaner.
Spark Plugs/wires
fuel filter
Cleaned MAF
Tried to get to 02s but could not due to corrossion...why I am taking it my mech.
The mileage has only gotten worse...was running 13.5-14 mpg.

Really frustrated...I will keep in touch and let you know if I find anything...do the same on your end please...thanks.

lee

i used a fuel cleaner additive (STP) with my last tank. before winter, i was geting 19-23 mpg. during winter, its dropped to 15-19.

i added that fuel cleaner and it actually improved gas mileage to 17-22 on the average.

i dont know if its due to where and when i was driving, etc, but it may have had an effect.

DOT3

I've got the same truck except 100% stock and I get 17-20 mpg. Closer to 17 in the winter. Make sure your MAF is clean.

X2and4X

mine is also stock. auto tho not a 5speed. 142k miles on her and it still gets 20mpg.

X-AWDriver

I've been getting 14-16 but I think I'm due for new plugs too but my current tank is looking good but I've been on the highway a bit more lately.

Rick F.

The fuel mileage on my 2000 took a step change around Thanksgiving from a monthly average of 19.5 to about 17.0. I DID put new rubber on and also went from 265/70/16 to 265/75/16, the latter having an additional 1.1" diameter. I expected a slight drop but not 2 - 2.5 mpg. I know for a fact that my average mileage always drops about 1 mpg in the winter.

A LOT has to do with your location, your style of driving and your mix of city/highway/backroads/terrain.

X-AWDriver

I have 265/75s on my truck too and I do have a lead foot but I've driven my mom's '99 around for a couple of weeks and I got better mileage with hers so I think I'm just due for a tuneup plus it'll be nice when we get the summer gas with no ethanol.

MTL_4runner

Here's a trio of good articles on the reasons behind the drop in fuel mileage during winter:
http://www.heavydutytrucking.com/2004/10/148a0410.asp
http://www.stretcher.com/stories/960812a.cfm
http://www.inct.net/~autotips/mpg.htm

Other than that just be sure to do the standard tune up stuff (air fliter, fuel filter, plugs, clean TB, clean MAF, run some top engine cleaner such as seafoam, change the diff fluids and do a tranny flush) then finally I would replace the front O2 sensor. Make sure all your tires are at the proper psi rating (I leave mine at 33-35) but on larger ones they may need lower pressure to maintain proper wear. At that point, it will run about as well as you can get it to run.

Alpine114

Listen, i know fuel milage goes down in winter. im running 265/75/16 on it now. "theryanator" let me know what your mechanic says. I work at Pep Boys, and have acess to alot of fuel addatives. these are all fine and dandy, but most of this stuff works for the time being. A good one i have come across was lucas fuel addative...they make great products. I just picked up bosch +4 plugs, and need to get them in. I went off roading, and ÅÅÅÅed up my Mass Air Flow Sensor a while back, but got it replaced by a local Toyota dealer. So i dont think thats the problem, unless there might be dirt in there. Also, with that, the copper elements of the MAF are fraggile, so i wouldnt want to mess with them too much...let me know what you guys find.

Alpine114

PLugs and O2 sensors havent been replaced, its got 74K on it right now....engine needs cleaned from splashed mud/water.....maybe another problem.......

MTL_4runner

Do not use Bosch plugs in your motor! They don't work nearly as well as OEM densos.
You can clean the MAF (will help mileage) but if it was truly damaged you should see a CEL.
You should do the O2 sensor again particularly if you have mileage problems.
I used to be a professional mechanic too btw.

Mad Chemist

Anybody got a part number on that front O2 sensor?

Alpine114

Yeah MLT, i meant NGK plugs, the Bosch +4 were for my 69 Cougar. but your saying the densos are better?. anyways, i had the MAF replaced,a bit ago. Possibly little dirt in new one, but most likely not. i really watched it this time around. If so, how would i go about cleaning that....and also the O2 sensor....is there one or two? i know theres one somewhere after the headers, but is there one closer to the block? And also, do you suggest i put Mobile 1 syn in diff. tran, ...??

MTL_4runner

OK thank god....Bosch are just trouble in for most jap vehicles (they kick butt on domestics and european vehicles). You can clean the MAF and do most of the rest of the maintenance by following this here (there are 5 pages worth of stuff to go through). There are (2) sensors on your vehicle, the front is an A/F sensor and the second (after the cat) is an O2 sensor. I would only recommend replacing the front sensor, the second one almost never goes bad or needs replacement as the first one gets all the exposure in front of the cat.

You can Mobil 1 synth but most on the board prefer Amsoil. I am sure either will be a marked improvement.

X-AWDriver

https://www.yotatech.com/forums/show...light=oil+poll

I think M1 is used more due to it's wide availability at most parts stores.