Good point, I'll reset the computer. As for spark plugs, they were new but after driving with this misfire who knows how the computer was compensating so I think I'll try that suggestion as well.

And I did some searching, is it true stock tire size for a SR5 is only 225/75/15?

I have 265/75/16 on mine which is almost 12% bigger. Is 10-12 MPG in winter still bad for that big of a tire or would that be normal and I basically don't have a problem?

 

what make, model, and size tires, and wheels do you have ?

 

Right above your post, I must have made it while you were typing lol.

99 4Runner SR5, 3.4V6, Auto, 265/75/16 All-terrains!

 

All Terrains, what specific brand and model ?


those things suck mileage. all reported mileage 17-19mpg is usually All season stock-sized road tires.
you put big meats on, mileage plummets

stock size is 265/75/16 (or 15)

 

MY 2002 Taco with 3.4V6, Auto, 265/75/16 All-terrains, gets 18 mpg(280miles on 15 gallons) in town and about 19-21 highway. normal driving no lead foot here...not sure if weight of Taco vs. 4Runner makes a big difference.

 

My 97 limited gets probably 15 mpg around town 19 highway right now. I have 265/75/16 BFgoodrich All Terrains on it. The stock size is 265/70/16 with the 16 inch wheel option from the factory.

 

Well.. This latest tank I'm on track for about 200 KM and when I fill it up it takes 55 litres...And since most of you are US guys that equates to 8.5 MPG.


SOOO....... I am going to buy an o2 sensor. If that doesn't work I am going to have a 4runner for sale becasue this is making me broke

 

How much is the O2 sensor going to cost you? Once installed, don't forget to reset the computer then run about 100 miles to allow it to readjust to new sensor then put a fulltank of gas and see what kind of mileage you get..

 

Probably around $100 locally... But I'm not all convinced that an o2 sensor will increase my mileage by 6-7 mpg so I don't have much hope lol.

 

K guys... Changed sensor, pulled fuse, drove alot, no change still horrible mileage.

And this is my wifes 4runner, she wants to trade it in for a jeep patriot or liberty if I don't fix it.

See it's an emergency now. I need to fix this fuel mileage problem or it's gone I don't want a jeep I need a miracle!

Is it possible, even though it shifts and works perfectly, that my transmission is the problem? The way I see it, it has to be something major to get 10 mpg and we are driving it as easy as possible. Not even using 4x4 at all for an entire tank.

 

MB4runner, you still haven't posted anything really relevant. Like I asked on previous page, how long in minutes does your engine take to go from ambient to 190F?

 

Around 5 minutes, it's plugged in, in an insulated garage. And I tested the mileage on the highway too, just straight highway driving, TPS reads fine, MAF reads fine, short term and long term fuel trim are slightly in the negative, which leads me to believe the proper fuel is being sent but something mechanical is causing it to need more power in general. And the brakes aren't dragging I checked that.

 

Are you saying you are able to keep 190F at highway speeds without the front being blanketed?

 

No, just normal driving in the city, I didn't pay attention on the highway, I just wanted to see if it got any better on the highway.

But there are tons of 4runners around and none of them drive with the front blanketed and they get way better mileage. The local dealerships even confirmed this but all they want to do is a tuneup even though it just had one. (Although I let them do the injector cleaning for $150, but I don't want to keep guessing at problems because it costs money)

Not to mention my 88 on 35's with stock gears gets better mileage. So I don't think it's the weather but I'm open to suggestions.

 

That is quite amazing then, my temperature went under 190 even at 10F to 5F, with the front end naked.

 

How do your plugs look? Are you running rich? If they are carbon fouled check your fuel pressure regulator and or coolant temp sensor. Also make sure that your engine is getting and staying hot enough that the ECM doesnt think the engine is cold and enriching your mixture. Do you know the specs for normal injector on time? If you have a bad fuel regulator the on times will be very short.

 

Well the thermostat is probably around a 185 isn't it, so it would control the temperature to be right around there so I don't know why it's amazing. And it's only -10 in the morning it warms up during the day to to 5-15



Plugs look like this:

These were supposedly a few months old put in by the previous owner. I don't really know how to read spark plugs but they look like they were all dry black and now white is forming on top...

 

The plug looks fine. Just stick a cardboard the size of the radiator between the rad and A/C condenser. Run it for a full tank and see what it does. All you have to lose is cost of cardboard.

 

plugs look new and good.

Good thing they have dual electrodes. It brings up an important fact that these trucks wil run like poop if using single ground. I've had auto parts stores give me the wrong ones, and their computer gives them the wrong part #. I couldn't imagine how many people probably just put them in w/o realizing they were the wrong.

 

Yeah they all look like that so it's good and like I said it had a full tuneup at toyota with all oem parts.

But like I said, it drives like a dream, perfect, just get horrible mileage. It's a real mystery. So what is it then, if the engine is fine, it's the transmission, or brakes or what?

Transmission is very smooth, rear wheels spin very freely, front ones have a little drag but people say thats normal for disc brakes. But how freely should the front spin when jacked up? (5 revolutions or 10 or how many?) (And even then, the truck is off, what if they start dragging only when it's on and gets the assist from the booster or something)

And I'll try the cardboard trick, I'm sure it will help a little but I don't see it getting me another 5-7 MPG.