cema

I took some time this weekend to do some preventative maintenance on my '05 King Ranch. I replaced my badly deteriorated windshield wipers, fixed some lights, cleaned the throttle body, put in a K&N drop in filter, and replaced the fuel filter. After all of this i unplugged the battery for about 1 min or 2. After doing 40 miles of driving the gas gauge has moved down about 15-20% and the "miles to empy" loses 3-5 miles every mile of actual driving. IDK what is going on. I have checked for leaks around the fuel filter. It is dry. no leaks at all around it. Truck says I am averagin 15.5 MPG and thats 85% in town driving.

WHERE IS MY GAS GOING??

Mod (Ret.)

15.5 MPG is good for a 5.4.

Was this type of driving more city then highway driving? An "average" has to be based on a longer driving period; 40 miles is not good enough to base an average on IMO.

BadFish523

I wish I was getting 15.5 mpg. I'm getting about 12 and that's 90% in town driving so I'm fairly happy. I can pull 15 on hwy. I would fully expect your mileage to drop as you add more miles to the average.

Ricktwuhk

What does unhooking your battery for a minute or two do? What was your goal in doing that?

What was your MPG before you did any maintenance?

As stated, 40 miles shows nothing.

Martian

Most likely was just trying to clear the MPG reader, but there are easier ways to accomplish that

BadFish523

My guess is trying to reset the computer and do the relearn process but I think it takes longer than 2 or 3 minutes to drain the power. I've always heard 30 minutes. He also never stated if he actually did the relearn process or just went about driving right away.

Martian

Nah, it doesn't take that long. I actually learned over the weekend that all you have to do is get close to the battery dying (i.e. low voltage) for a short amount of time and everything gets reset. PCM probably has low voltage protection.

Ricktwuhk

I know what could be accomplished by disconnecting for a specified period, suspect the OP did not. For example, having an electronic transmission relearn shift points.

Martian

Wasn't trying to insult your intelligence, Rick.

Mod (Ret.)

I've always removed both the positive and negative cable from the battery, then touched the two cables together. Causes anything within the truck that stores a minute charge to instantly drain.

A radio repair shop told me this as a last resort to removing stuck disks in the factory radios or NAV units; it worked on my factory NAV unit that would not spit out the navigation disk after going through the steps to eject it via the menu.