Super bad fuel economy, and other questions

[speeding_infraction]

Hello all

1. A few weeks ago I got the fuel transfer system replaced (pump, filter etc). Previously I had been getting, by my estimation, 11-13mpg, about 150-170 miles to the tank (18gal). Now i am getting about 130 miles to the tank, which seems like a big difference. I have noticed that since these parts were replaced, it has really struggled keeping a decent idle on hot starts (will go up to about 500-750 rpm and drop down to about 250 rpm and than go back for a minute). It didn't used to do that. My driving style hasn't changed. Truck is basically stock (similar size tires, no lift). For exhaust, it has a pacesetter 6-2-1 and than starightpipe to a fairly quiet  muffler. No cat. How can I improve my fuel economy/what changed? Why did it get so bad?

 

2. How much work goes into installing lunchbox lockers? 

 

3. Will doing a cold air intake make my fuel economy better?

 

[VorTekX]

Maybe your O2 sensor went bad? Is the fuel intake system the only thing you changed before starting it up again? 11-13 MPG is still pretty low assuming you have a stock setup regarding wheels. 

[gogmorgo]

If it was running lean due to a failing fuel pump then yes, fuel consumption will increase. 
Something is definitely up with that idle speed. Is the truck still stock? Cruiser’s tips at cruiser54.com are a good starting place. 

[speeding_infraction]

14 minutes ago, gogmorgo said:

If it was running lean due to a failing fuel pump then yes, fuel consumption will increase. 
Something is definitely up with that idle speed. Is the truck still stock? Cruiser’s tips at cruiser54.com are a good starting place. 

Upgrades include: 4.0 HO head, HO intake manifold, and the header I mentioned. The fuel pump wasn't always bad. 

[speeding_infraction]

1 hour ago, yungupgrade said:

Maybe your O2 sensor went bad? Is the fuel intake system the only thing you changed before starting it up again? 11-13 MPG is still pretty low assuming you have a stock setup regarding wheels. 

I will replace it and follow up. Also going to do cruiser's list of tips that apply

[VorTekX]

Go through as many of cruisers tips as possible before replacing the O2 sensor. The 02 sensors are sold on rock auto, you want an upstream sensor. How many miles does your truck have? Usually need to replace the sensor around 80k.

[speeding_infraction]

My truck has 165k miles on it. Will start on the tips tomorrow. 

[cruiser54]

Tips 1,3,4 and 5 are the most important at this point. 

 

[speeding_infraction]

13 hours ago, cruiser54 said:

Tips 1,3,4 and 5 are the most important at this point. 

What are you using for MAP sensor vacuum source? Throttle body HO? TPS used? 

Not sure what you mean about the MAP sensor. Whats the difference between renix and HO throttle bodies? Also don't know about the tps. Never changed it. 

[speeding_infraction]

There's a vacuum gauge on my dash, is that what your asking? At idle it reads between 15-20

[cruiser54]

All my Tips are at www.cruiser54.com. 

 

 

[speeding_infraction]

K I'll check em out

[speeding_infraction]

Working on tip number 1, I found this:

Obviously it will need replaced. I looked up the part on Napa online and the replacement has an extra small cable on it which mine doesn't. Is it still okay to use?

https://www.napaonline.com/en/p/MPB781107

[speeding_infraction]

My current cable is 39" and the replacement is stated to be 45"

[speeding_infraction]

Got it fixed nevermind 

[VorTekX]

1 hour ago, TurboedMJ said:

Got it fixed nevermind 

If you're upgrading the battery cables there's a "big 7" kit on jeepcables.com

[pizzaman09]

If you buy an O2 sensor, get the NTK branded sensor.  I first tried Bosch and it didn't perform well, I gained a lot of power and smoothness back switching to the NTK.

[speeding_infraction]

My throttle body measures 60mm. The TPS doesn't have letters on it, so I tested the middle wire and it read about 50.6/7 ohms. The value changed 0.1ohms when I shook the harness next to the valve cover. 

[speeding_infraction]

[speeding_infraction]

Also, replaced the O2 sensor. The old one was completely black when I took it out. It seems to run a little smoother now, not sure if that's my imagination though. 

[cruiser54]

Does the engine harness have the letters on it? 

[speeding_infraction]

I will check. 

[speeding_infraction]

I looked and didn't see any lettering but I checked the other twowires and they both read zero. 

[cruiser54]

Strange. Use a magnifying glass. 

[speeding_infraction]

I looked again and didn't see anything.