Poor gas mileage

2014 TRD Sport 4-door short bed
4.0L V6 automatic
Stock other than magnaflow exhaust that dumps before rear axle.

Truck got 18mpg-21mpg when i first got it. Over time the gas mileage had dropped to about 15mpg-16mpg. Four months ago gas mileage went from getting about 15mpg-16mpg to 11mpg-12mpg. I've since changed the spark plugs and air filter. Tires have been at 30lbs consistently since before the gas mileage dropped. It doesn't make a difference if I'm on the highway or surface streets. I've tried driving slower, normal, faster, traction control on, traction control off. I hadn't changed anything at all when the gas mileage dropped. Also haven't changed anything since i got the truck. No check engine light.

My only other idea was to clean the MAF sensor. What else can i check/clean/change/fix?

 

Brakes, hot lug nuts after a drive. Alignment, uneven tire wear. Check out the threads on this the last couple of days for more ideas

 

Definitely clean the maf

Get your hands on a little code reader and look at the long/short fuel trims

 

Four monthes l would blame winter gas for part if it. Definitely clean the MAF sensor. I'm going to assume that no codes have been thrown.
Could be an Oxygen sensor starting to slowly go.
What is your trucks mileage?

 

Clean maf and throttle body, check O2 sensors

 

How and what are you using to measure your gas mileage ?

 

Probably just driving 20 miles to refill

 

Don't clean the MAF unless you're getting actual MAF symptoms. The MAF will not cause fuel mileage issues without tossing a bank lean code because the O2 sensor will compensate fuel to bring it back to stoich. Even then a MAF doesn't make the truck run rich (e.g. poor fuel mileage) unless it's defective. Dirty MAF will only cause lean codes 99.9% of the time because the reference wire is not out in the open to get dirty.

The MAF has a coating on the wire that is easily damaged and used to make me a lot of money when people thought they could just clean it all the time like it made fuckall difference.

Also, fuel trim is only a measure of the bias in the system. The O2 will always bring it back to the middle and trim has zero impact on fuel economy unless it's pegged which, again, will toss a code.

 

Is that the answer you give a customer when they ask you about the fuel milage on their rig?

How would you tackle a poor fuel mileage complaint?

 

Yep! Here is the link

https://www.tacomaworld.com/threads/very-bad-gas-mileage-in-my-truck-advice-needed.612629/

 

On the MAF? Every time. The only time you clean one is if you get a bank x lean code and don't have the cash to replace it. If you clean it, you'll see that vehicle back in a few months with the same problem. If it's getting nasty frequently then you need to get a heavier service air filter or dump the K7N style oiled filter - if my dad can drive his F150 around a cement plant all day 5 days a week without issues but once every 50k, a dirty MAF shouldn't be an issue for most people but once or twice during the ownership of the vehicle.

Fuel economy issues are about 90% of the time indirectly on the customer and painfully obvious the other 10% of the time. Normally, it's something like poor ignition, brakes dragging, slow switching O2 sensors... basically anything that will cause a subtle loss of power or parasitic loss over time that the customer doesn't realize they're putting more foot into it than usual. You start with the basics checking sensors for normal operation then go from there.

 

So your're saying cleaning doesnt do anything, just use less gas pedal? Even when it dropped from 18-21 all the way down to 11-14?

I would think that a dirty maf would underreport, the 02s would see the extra air and the pcm would add more fuel than needed.

Which sensors can malfunction and affect fuel mileage without coding?

 

Try running Seafoam before you do anything else. I would put 2 cans in with a full tank. Make sure you are calculating mileage correctly. Fill tank and reset trip meter. When it needs to be filled up fill the tank and let it shut off automatically at the nozzle. You will divide miles by gallons recorded. Do the simple things first. Most people don't know how to properly calculate MPG.

 

2015 dcsb 4x4 4.0
Get 20 to 21 mpg ever tank for the last 105k miles

 

Pump up your tires to 36 psi

Also, use engine braking more and less brake pedal

 

The long fuel trims are 4% for bank one and 8% for bank two. Also the exhaust is starting to kinda sound like a kazoo...

 

Those trims aren't excessive.. did you clean the maf?

 

Did you air up your tires to 35-36 psi?

I would say 15-17mpg Is kinda normal for these trucks unless you spend every mile on the highway. The drop after that is the strange part.

How many miles on your truck?