Question about low MPG

N

nissanh

Senior Member
My 4runner V6 4X4 gas gauge is coming down (visible) even after driving 6-8 miles. No CEL.

For the past 3 weeks I did no more than 25 miles with each trip about 4 miles max. Tank level has come down from half to quarter. On highway it do 17.5 MPG max.

Any suggestions?

Still have the original O2 sensors and have CA emissions on it. Can I increase the mpg if I changed the O2 sensors pre and post?

New Air filter (denso)
New Spark plugs (NGK)
Original spark plug wires still (180 K miles)
 
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Take your map distance and figure out the mpg, if it's not the same as what your truck is telling you, could be a fuel unit. Could just need som TLC with some O2 sensors, maybe a good tune-up, I get above 20mpg.
 
Im guessing your gas gauge isnt reading correctly. Does it drop noticeable mainly from half a tank to quarter? Have you filled up and calculated your mpgs from a full tank since? Possibly just have a bad fuel sending unit.
 
kinda hijack the thread real quick? whats the normal readout values for bank 1 and bank 2 O2 sensors? one is usually around.999 the other varies in between .7 and .2, (normal .5)
 
SilentYoda3 said:
Take your map distance and figure out the mpg, if it's not the same as what your truck is telling you, could be a fuel unit. Could just need som TLC with some O2 sensors, maybe a good tune-up, I get above 20mpg.
Click to expand...

TLC with O2 sensors? Can we clean the TLC? Like to know how to do this.

Tuneup? Have clean throttle body, new OEM filters all around and NGK plugs. missing anything?

What do you mean by the fuel sending unit? Is it the fuel pump or the actual fuel gauge inside the instrument cluster?

Gas gauge is dropping gradually and after 8 mile trip I see the gauge about few degrees below it started. Never seen it like this before.

How do I check the reading in the O2 sensors? How many O2 sensors a 5vzfe has? I though 2, pre and post cat.

I'll try to fill up and calculate the mileage with the trip counter and # of gallons it took.

In the mean time I like to know things I can check/improve

Thanks guys.
 
nissanh said:
TLC with O2 sensors? Can we clean the TLC? Like to know how to do this.

Tuneup? Have clean throttle body, new OEM filters all around and NGK plugs. missing anything?

What do you mean by the fuel sending unit? Is it the fuel pump or the actual fuel gauge inside the instrument cluster?

Gas gauge is dropping gradually and after 8 mile trip I see the gauge about few degrees below it started. Never seen it like this before.

How do I check the reading in the O2 sensors? How many O2 sensors a 5vzfe has? I though 2, pre and post cat.

I'll try to fill up and calculate the mileage with the trip counter and # of gallons it took.

In the mean time I like to know things I can check/improve

Thanks guys.
Click to expand...

He means TLC as "tender loving care". He's sayin to replace the o2 sensors. I'd pull em out and check em and check for dirtiness/black marks. Yes there are two, pre and post cat.

The fuel sending unit is in the gas tank. It's what tells the gauge how much gas you have. The symptom your having could just be your fuel sending unit going out, and the gauge is just giving you a false reading. That's why you should calculate your mileage.

I had to replace mine, it wasn't too hard. OEM fuel sending unit was around $160
 
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I am just going to throw this out there:

Normal MPG is 15/19 city/hwy in a V6 4Runner.

Depending on how I drive, sometimes I get 15 in the city, sometimes I get 17.

Unless you are consistently getting less than 15 it may be operating normally.

Source: fueleconomy.gov
 
downpour11 said:
He means TLC as "tender loving care". He's sayin to replace the o2 sensors. I'd pull em out and check em and check for dirtiness/black marks. Yes there are two, pre and post cat.

The fuel sending unit is in the gas tank. It's what tells the gauge how much gas you have. The symptom your having could just be your fuel sending unit going out, and the gauge is just giving you a false reading. That's why you should calculate your mileage.

I had to replace mine, it wasn't too hard. OEM fuel sending unit was around $160
Click to expand...

Thanks for the clarification. I types TLC in place of O2 sensor.

OK, I'll remove the O2 sensors and clean the two. Can I use a metal brush to clean?
Would you rely on the DENSO O2 sensors sold on ebay?

I'll get back once I calculate the MPG manually.
Thanks guys
 
with mixed driving i get about 20mpg and on the highway i get about 22mpg.

Yeah sorry about that Nissanh tlc=tender loving care as pointed out. It's never really a bad idea to replace the O2 sensors in my opinion. Even if it doesn't help your mileage your truck will run better. But i'd start by trying to see if that fuel sending unit is bad, only time i've ever seen a gas gauge visibly drop was in my 1983 bronco when i floored it :trophy::trophy::trophy:
 
SilentYoda3 said:
with mixed driving i get about 20mpg and on the highway i get about 22mpg.

Yeah sorry about that Nissanh tlc=tender loving care as pointed out. It's never really a bad idea to replace the O2 sensors in my opinion. Even if it doesn't help your mileage your truck will run better. But i'd start by trying to see if that fuel sending unit is bad, only time i've ever seen a gas gauge visibly drop was in my 1983 bronco when i floored it :trophy::trophy::trophy:
Click to expand...

except new o2 sensors are like $100+ each lol which sucks!
 
Bought my o2 sensors for about $150--check amazon, rockauto or partsgeek--with partsgeek make sure you have the right part # because (in my opinion) their customer services sucks. I notice that with sort trips the Runner doesn't get the best MPG and I will notice the gauge moving quicker, take it out for 10 plus miles and my MPG is much improved. I had the truck in for state inspection last tank and I could tell I lost MPG because the truck didn't get a chance to run. MPG's do have a lot to do with how the you drive and using your brakes is the worst thing. Good luck.
 
Just had a drive in city.

Filled the gas tank all the way to the top with extreme patience. Basically spent about 5 minutes to fill the last part of the tank.

Did 13.1 miles and refilled from the same gas pump to the top with slow flow to get all the trapped air out. All I can put was 0.707 gallons.

That's 18.714 MPG in the CITY. I know this is too much, but 16, I'll take it. Much better than I assumed 10 MPG in the city.

Thanks guys... I'll keep my 4runner and will stop looking for 4cylinder 4runners :-)
 
1. You can't really clean O2 sensors. The actual sensor wire is hidden deep inside. Scrubbing on the outer casing won't help.
2. Only the first O2 sensor helps with MPG. It's used to calculate your AFR.
- The second is used to ensure that your cat(s) work.
3. Air filter. Replacing it should help - but not all that much. No need to get fancy, a paper air filter will work fine.
 
agloukhoff said:
1. You can't really clean O2 sensors. The actual sensor wire is hidden deep inside. Scrubbing on the outer casing won't help.
2. Only the first O2 sensor helps with MPG. It's used to calculate your AFR.
- The second is used to ensure that your cat(s) work.
3. Air filter. Replacing it should help - but not all that much. No need to get fancy, a paper air filter will work fine.
Click to expand...

Found this one on ebay. Denso O2 sensor

http://www.ebay.com/itm/DENSO-TOYOT...el:4Runner&hash=item3a7d5ecbf5&vxp=mtr&_uhb=1

Are the O2 sensors going in the front and after the cat same?

So there is only 1 O2 sensor before the CAT correct?

I have TOYOTA air filter about 6 months (3000 miles) old

thanks
 
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nissanh said:
Found this one on ebay. Denso O2 sensor

Denso Toyota 234 4162 O2 Oxygen Sensor | eBay

Are the O2 sensors going in the front and after the cat same?

So there is only 1 O2 sensor before the CAT correct?

I have TOYOTA air filter about 6 months (3000 miles) old

thanks
Click to expand...

Go here to get the correct Denso part number, THEN go to Amazon to buy it. On Cali.s, the before cat sensor is a wideband Air/Fuel sensor, the after cat sensor is a normal o2 sensor. They are not even remotely similar.
 
TheDurk said:
Go here to get the correct Denso part number, THEN go to Amazon to buy it. On Cali.s, the before cat sensor is a wideband Air/Fuel sensor, the after cat sensor is a normal o2 sensor. They are not even remotely similar.
Click to expand...

Thanks for the info. I looked at the site you given and the VIN is N for all and I do not see Cali version.
 
Around we go! Happens every winter. In summer months, I normally see my average FE between 19 and 22, depending on the driving. In winter, it drops fairly dramatically, down to between 15 and 17.

Right now, I'm getting the worst FE ever...just barely 15. Cold weather, snow, using Multi-mode and 4WD, and of course the winter fuel with less energy per unit.
 
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