Why am I gettin such bad gas mileage?

[jmt2404]

Ok so I have a 97 4runner limited with a NEW rebuilt motor. It has maybe 3000 miles on it. I get 180 miles to a tank of gas. Its bs.. When I moved here I was pulling a trailer and I got around 250 miles to a tank. How does that work? Granted it was before my lift and mod'ing started... but It shouldnt effect it that much should it?

Here are my theories on why I am getting such bad gas mileage..

1) I have read some where that a bad fan clutch can effect your gas mileage. And I think mine is going bad if not already bad...

2) This may be the biggest reason for the change.. I installed high flow injectors and a high flow fuel pump. They are both made by venom and not sure how much they are suppose to change.

Any advise would be very helpful.. thanks

 

[YotaZach85]

Why did you put in a higher output injectors and pump?

 

[eplanajr]

Why do you have aftermarket injects on your rig? Stock injectors should be fine for stock engine requirements...

With those injectors, you're computer needs to know what its using to feed the engine, so if you change the injectors you are messing with the entire system.

I say put stock injectors back on, then do the usual stuff like check the plugs, wires, fuel filter, clean the maf, etc.

 

[98OzarksRunner]

What they said. If you change to higher flow injectors the engine mangement computer has to be re-calibrated or too much fuel will flow. The amount of flow is based on the injector pulse width. Same pulse width, larger injector means too much fuel. Poor gas mileage, oil contamination, and excessive cylinder wear can result. The only reason to go to larger injectors is if you have a supercharger/turbocharger or using nitrous (or change to E85), all of which will require a retune of the computer.

 

[YotaZach85]

Why do you have aftermarket injects on your rig? Stock injectors should be fine for stock engine requirements...

With those injectors, you're computer needs to know what its using to feed the engine, so if you change the injectors you are messing with the entire system.

I say put stock injectors back on, then do the usual stuff like check the plugs, wires, fuel filter, clean the maf, etc.

There it is! If you're trying to compensate fuel for the minor air upgrades you have done you're actually working backwards. You can leave the upgraded pump in unless you messed with the stock fuel pressure regulator but those injectors have to go.

 

[sportscarfan]

285/75's theoretically have 6.7% more rollout than a stock 265/75 tire. So if you see 180 miles on the odo., multiply that by 1.067 to get closer to the actual miles traveled.
180*1.067=192.6

How many gallons does it take when you fill it?

 

[jmt2404]

Ok

Ok thats all I need to know really.. I wasnt sure how much difference the injectors made. But it def makes sense about having to retune the computer. The reason for me putting the injectors on there were becuase I was going to get the heads port and polished. But then I had to replace the engine and it didnt happen. So I will go back to my stock injectors and see what kind of difference it makes.. thanks guys..

And thats some good math. I didnt realize it would add that much to the actual mileage. And to answer your question I add around 14 gallons every time I fill up..