Terrible gas mileage

[wrangler8]

I have a Ranger xlt std cab, 3.0 v6, 4x4 truck that I recently purchased. When it had stock tires it got about 14 mpg which is pretty bad. Then I bought some 31x10.50 mudstars and put them on the truck. I was expecting worse gas mileage but now its really bad. probably like 10-11 mpg. engine has been sluggish ever since I bought it but it runs good. Any feed back on potential issue or what I could do to help mpg?

 

[tmcalavy]

Stock tires...you mean 14's? If so, 14 mpg sux with stock tires. You can change the rear gearing to better suit your bigger tires, but I would start by pulling the codes, doing a basic tune-up and measuring mpg by mileage logged divided by gas consumed (measure at the pump). The former owner could have swapped gears...if so, your mileage and trip odometer may be off...giving you the low mpg reading.

 

[swynx]

I had shitty gas mileage with my 4.0. 2.5 miles to work. So 5 round trip. I could use a 1/4 tank per night. Replaced 02 sensors. Fpr. Tps. Iac. Maf. Etcs. Fuel pump. New coil. Wires. Went from like a 27ish tire to 31x10. 5 now I get about 17. And that's while driving like an ass hat. Full throttle there and back.

If you've got the know how and the cash. And if this truck is going to be an investment to you. Replace everything I mentioned. All of those things made my truck drive better. Go faster. Run smoother. And better mileage. My fuel pressure regulator was clogged so it made the most improvement.

 

[wrangler8]

I was getting 14 mpg with stock tires. i think they were 225/70/15r or something like that.
what is ''pulling codes'' mean? I have changed 02 sensor, distributor cap, spark plugs, fuel filter. dont know if that is supposed to help, but apparently not.

 

[RonD]

When electronic fuel injection was added to engines a simple computer was needed as well, since a computer would be added an On Board Diagnostic(OBD) software was added as well.
Ford calls their computer a PCM(power control module), or EEC(electronic engine control)
Pre-'95-'96 car/trucks use what is called OBD I(OBD one), post-'95-'96 use OBD II

Both OBDs have ports you can plug an OBD reader into and get "codes" that will give you information about the system.

OBD I is pretty simple software and you can use a jumper wire to read codes via a flashing light, or use an OBD I reader.
OBD II has more information available, and you can only use an OBD II reader.

The Readers are not interchangeable.

 

[snake]

What kind of plugs did you use? I strongly suggest motorcraft parts- I just did an engine swap on a 01 4.2 in a f-150. The oil filter got loose and the engine seized. Customer brought me a factory rebuilt long block. The plugs from the old engine looked original at 207K- five were still motorcraft one was a bosch, obvious replacement to correct a miss. The 5 factory plugs were kinda jacked but relatively clean, that bosch was packed with carbon (white, so it was firing properly) looked 10 times worse than the factory plugs with probably 150K less miles on it. This may not be your issue, but a lot of times tuning up with bastard parts brings on more problems than it solves.

 

[tmcalavy]

Codes tell you when one of truck's systems has a fault, like a bad sensor...which can affect mpg quite a bit. The auto parts stores will put a code reader on it and pull the codes for free.