Bad gas mileage

[Commanche2]

Hello , 

   I have a rebuilt 4.0 Comanche 2 wheel drive . 11 mpg in winter ! Also bench seat has a hole in it .... can’t find a good cover .

  I’ve tried 195 thermostat anything else I can do? 

[Jesse J]

Just now, Commanche2 said:

 Also bench seat has a hole in it .... can’t find a good cover .

 

link in sig! the plan is to start making them for people. I just need to finish up my interior then I will figure out pricing and logistics

[89 MJ]

It is typical for vehicles to get slightly worse fuel mileage in the wintertime, but I think your fuel mileage is off. Does your truck seem to run rich at all? What size tires and gears do you have? What is your driving style?

[Commanche2]

IDK my brother bought the truck brand new in 1987 first year for 4.0,and it had 178k on original motor before I swapped for an Exteme machine long block from Lake Tahoe ,Cali.,its a 1/2 ton truck and I`ve had over a ton on it .It`s a long bed i have platinum plugs ,new injectors . also the pigtail wiring and ballast resistor was missing from the factory for the auxiliary fan ,so i have it rigged to a switch. more than likely lower rear end gears,and is probably running rich.  235-75-15 Bridgestone Deulers on stock steel rims for winter

Edited March 3, 2021 by Commanche2
left out tire size

[89 MJ]

Hmmmmmm, let's start with pulling the spark plugs and looking to see how those look. How are you getting your MPG reading? If you are doing it by your odometer and dividing that by the number of gallons you put in, your reading might be off if your speedometer is off at all.

[driveslowsnackoften]

I had awful gas mileage until I realized I had knocked the vacuum line out of the MAP sensor. Was like flipped the Fixed/Broken switch. Maybe give that line a looking over.

[jdog]

On 3/3/2021 at 10:10 AM, Commanche2 said:

platinum plugs

These motors hate these plugs.

When was the last time you changed the 02 sensor?

[Pete M]

plain jane copper plugs do work best  

[Pete M]

also raybuck.com makes seatcovers for certain benches.

[cruiser54]

Have you completed Tips 1 through 5 at www.cruiser54.com?

 

Copper plugs are fine. How old are the plug wires, cap, and rotor? Should be replaced every 30,000 miles like the plugs.