Poor Fuel Economy

I have a 2011 Tundra 4.6 liter, I was getting 18-22mpg, all the sudden I have dropped to 11.94mpg. Cleaned the MAF sensor, new air filter, cleaned the throttle body, ran a can of Sea foam through the gas tank. I am thinking O2 sensors, does any one have any other ideas? Which of the 3 O2 sensors controls the most fuel economy?

 

Somebody else on here had this happen recently, and they found that one of their brake calipers was seized up. Maybe check that.

 

Just got under the truck it has 4 O2 sensors, I do have a brake light on also so I will check the Calipers. Any other ideas are welcome. Thank you

 

A sticking caliper should make it pull to the side pretty hard and you would probably smell the hot brakes.

 

So I have been looking at Rock auto for O2 sensors. I found 4 under my truck but can't find any diagram/info that shows all 4 sensors. Does anyone have a better place to find any info?
My truck does pull a little to the right but not bad enough to say a caliper is stuck.

 

One thing I learned the hard way. If you are replacing O2 sensors replace them all and replace them with an OE brand! Do it once...

 

Do you have a infrared thermometer? If you do go for a drive and check each brake rotor individually. It won’t pull very much necessarily if it’s one of the rears. You say it is pulling lightly. A little bit goes a long way.

 

Just shot all 4 wheels with the IR gun nothing sticks out as super hot. I did notice today that idling at the stop light I could feel the truck idling funny. Felt like it was almost cutting out, I will have to find all 4 o2 sensors and go that route next unless there are other ideas?

 

All of the O2 sensors are with the second diagram as you scroll towards the bottom. Have you looked at the throttle body and MAF? My throttle body was gummed up on the back side at 62,000 miles and caused my idle to surge.
https://www.sparksparts.com/auto-pa.../emission-system-cat/emission-components-scat

 

Why don’t you pull out a spark plug or two and see how they look. Before you go throwing money at 02 sensors.

 

@ARamirez73 has answers

 

Thanks for the help everyone, I will let you know what the truck is doing after I do all the O2 sensors.

 

So I pulled and replaced all the plugs, new O2 sensors, took it to a shop had them put it on a machine and nothing is wrong according to the machine. All the fuel to air ration is correct, all sensors reading good. I am still getting 11.98 MPG compared to 19 MPG 5 weeks ago. Throttle body cleans, MAF sensor cleaned, I have good compression on all cylinders. Any other ideas out there?

 

Have you checked to make sure a caliper isn't seized, or your alignment isn't messed up and you are plowing.

 

Just pretend you have a 5.7 and it will be right....

But in all seriousness have you hand calculated MPG or just went off of the computer?

 

Are you Flexfuel?

 

Not Flex Fuel, I always hand calculate, my truck is not equipped with much as far as technology pretty plain Jane Tundra. Just had it aligned last week no calipers sticking, had new rear brakes put on yesterday since it was in the shop. I am seriously running out of ideas, I guess unless I get lucky I will have to wait for something to break and give a code.

 

Shot in the dark. Maybe unplug the battery for 20 minutes and hit the break pedal a couple times to make sure everything resets. Longshot

 

Do you have reduced throttle at all?

Catalytic Convertor comes to mind

 

At time it feels like I have reduced throttle, but I took the truck for 1000 mile trip got 13.12 MPG on the way there, 14.59 on the way back at 80 MPH. Now I am back in town getting the 11.92 MPG again. The truck has been hooked up to the computer at a shop 4 times in 2 weeks no codes, nothing wrong as far as they can find.

 

OP, did you try this yet? Here's why I ask. I was getting 14mpg on the hwy recently on a trip to Athens GA. 75 mph and under, cruise control, not a heavy foot. No mods on my 2018 CM 5.7 4x4 OR, all stock. I've noticed over the last 3-4 months my mileage slowly started going down, hand calculated. Usually 18 on the HWY, to 14. When in Athens, I unplugged my negative terminal for about 30 minutes, which reset the ECU and immediately my mileage went back up. On the way home from Athens, 18.2 MPG, hand calculated. That was in January 2019. My in-town mileage is around 14.5 or so, but that's expected. This may or may not work, and for some reason, it may still be an issue for me over time. But I've never done any mods to my truck, use different gas stations for fuel so I can't explain why this happened to me. I've heard of other folks having the same issue and it was cleared up by doing this. Try it, you have nothing to lose.

 

Try not using the onboard mpg readout. Zero out one of your trip meters and just hand calculate when you fill up like others have said. What do you normally get over the course of a tank? How many miles does your truck have?

 

Unhooked for about an hour, we will find out tomorrow I have a 280 mile trip so hopefully my MPG is back, fingers crossed. Thanks for all the help and suggestions, I will post the results later tomorrow. Again thanks to everyone.

 

Maybe it’s trying to tell you it’s time for an oil change

 

I hope not since this oil only has 2K on it.

 

Fuel filter.

Fuel injectors.

May be clogged/dirty.

 

Possibly a wheel bearing? I watched a guy jack a vehicle up in a shop and he spun the wheels slowly one at a time while listening to the hub with a stethoscope. It is possible that a wheel bearing is dragging?
Having just purchased a 2015 Tundra with a 4.6 L I am just happy to hear that you were getting 18-22.

 

15whtrd said was correct resetting the ECU worked. I drove 78-79 MPH all trip and got 17.91 MPG. Thanks.

 

So resetting the ECU was the fixer?

 

Yes sir