Thought for sure the MAF was the reason for my terrible gas mileage

[68whiskey]

I've been getting around 10mpg lately. Part of that is the use of 4WD and idling to warm up before driving, but it cannot be that bad for just that reason. Before it got cold and started snowing, I was still only getting 13 mpg. With newer plugs/wires I thought the MAF had to be filthy. Well, I guess that's not the reason with how clean it is. Back to the drawing board.

 

[alumarine]

Under the same circumstances, lots of idling and 4WD I got 11.5 mpg last fill.
That's normal for me when it's cold and mine is in good tune.

 

[habanero]

If you're referring to the air temp sensor in the pic that's not the wires you're looking for.

 

[68whiskey]

Under the same circumstances, lots of idling and 4WD I got 11.5 mpg last fill.
That's normal for me when it's cold and mine is in good tune.

I guess it's just hard to imagine getting mpg that low. Although I don't enjoy the fact that you're getting terrible mileage like me, it's nice knowing I'm not alone haha

 

[68whiskey]

If you're referring to the air temp sensor in the pic that's not the wires you're looking for.

I was expecting the hot wire to be filthy, and as you can see it's clean. I was just hoping for an easy scapegoat.

 

[habanero]

I was expecting the hot wire to be filthy, and as you can see it's clean. I was just hoping for an easy scapegoat.

That particular sensor in my husband's 99 was in great shape, but the wires for the MAF were so black it took some looking to find them. The PO had been running an overly-oiled K&N.

 

[kball]

You need the clean the little wires down inside. Here's both 96-98 and 99-02 styles.

 

[T4R2014]

I'm getting the same mileage and it doesn't surprise me. If fuel economy scared me that much I wouldn't have it(or two for that matter).

 

[68whiskey]

You need the clean the little wires down inside. Here's both 96-98 and 99-02 styles.

Thank you! I appreciate it. I'll pull it back off and get these. I got everything pretty good but honestly completely forgot about these.

 

[68whiskey]

I'm getting the same mileage and it doesn't surprise me. If fuel economy scared me that much I wouldn't have it(or two for that matter).

Don't get me wrong, I didn't buy a third gen 4Runner because I expected/care about great mileage. I just didn't expect numbers that low to be honest, so I'm looking at things that may need cleaned/replaced. That's all.

 

[alumarine]

With my 2cnd gens I'd be in the 9's sometimes when it was cold.
Actually we just had a week of -25 here so expect to be less than 10 with my 2000.

 

[rideexileex]

Have you replaced the upstream O2 sensor? That is what made the biggest 2 mpg difference for me in the past. Even with all my weight / tires, I can get 18mpg highway.

 

[diverscale]

seconded on the 02 sensor. Might not be your case, but when I bought the truck, I was getting bad gas mileage, and acceleration was somewhat sluggish, but not enough so you could notice in city driving.

I isolated the problem to be the o2 sensor voltage. I changed both with denso, which made a great difference.

 

[PWD4R]

If something was wonky with a sensor then you'd get a code or a check engine light. Honestly, winter fuel is way worse than summer. And plus when you idle to warm it up it takes longer and revs high for a longer period of time. 4WD doesn't affect my mileage too much (still get a tank average of 13-14 when spending a full day in 4 Lo (about 18-20 miles))
I would reassess this in March or April to see

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[gamefreakgc]

O2 sensors don't fail instantly, they slowly wear out over time. They are supposed to last about 90k miles per Toyota, but after a while they get lots of sediment and don't read as well as they used to. Changing the upstream one can make a difference.

 

[BoomSticks]

If something was wonky with a sensor then you'd get a code or a check engine light.

Not necessarily, it's really common for bad O2 sensors to not cause the computer to throw a code.

WHAT THE HOME MECHANIC NEEDS TO KNOW ABOUT O2 SENSORS

 

[diverscale]

If something was wonky with a sensor then you'd get a code or a check engine light. Honestly, winter fuel is way worse than summer. And plus when you idle to warm it up it takes longer and revs high for a longer period of time. 4WD doesn't affect my mileage too much (still get a tank average of 13-14 when spending a full day in 4 Lo (about 18-20 miles))
I would reassess this in March or April to see

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Not at all. If the sensor totally fail, yes, you will get a code, but most of the time, you will NOT get a code. Mine were throwing totally out of tolerance voltages, and I did not get any CEL. I've also seen this behaviour on many other cars too. Stop spreading false information thank you.

 

[PWD4R]

Not at all. If the sensor totally fail, yes, you will get a code, but most of the time, you will NOT get a code. Mine were throwing totally out of tolerance voltages, and I did not get any CEL. I've also seen this behaviour on many other cars too. Stop spreading false information thank you.

A reply was already addressed so thanks for nothing lol. Also it doesn't have to completely fail smart one. A simple dirty MAF can throw a code. Internet bad ass over here.. lol.

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[BamaDrewski]

O2 sensors don't fail instantly, they slowly wear out over time. They are supposed to last about 90k miles per Toyota, but after a while they get lots of sediment and don't read as well as they used to. Changing the upstream one can make a difference.

The O2 sensors are tricky little things cause they rarely throw a code. If you replace them, I would recommend you replace both. I bought my DENSO's on Amazon. On a Non-California version T4R like mine, the part number is the same both front and back: DENSO#: 234-4162. Don't make the same mistake I did and trust Amazon's part look-up feature. They show a different )2 for the front and another for the back. That is incorrect!

Changing the spark plugs (Toyota OE Plugs!) is also a cheap way to see if it improves your mileage.

Also, fill her up, disconnect the battery for a few minutes and let the ECU reset. Run a tank through (mileage won't be great after the re-set) but the 2nd tank usually gets you to a solid idea of what mileage you will get overall.