Gas mileage problems!

Chris97K1500 · July 31, 2003

Okay, I recently put on a Body lift and disconnected the battery during the install. It was disconnected for about 10 hours. After reconnecting it and driving around I noticed that I was getting much more mileage out of my gas. To the point where I thought the gas needle was broken. Once I got to about 140 miles it started to go down, and when it got to 260 I filled it up and to my surprise I could only hold 13.7 gallons, which the gauge read that I had a half tank left. I was getting about 19mpg (usually 14 no matter how and where I drive). At that point I was thinking it must have been the resetting of the computer that is causing me to get this great mpg. Since it's gone back down to around 14mpg My question deals with disconnecting the battery after each fillup, what harm would this do to the engine. It must be burning the gas at a different rate after the disconnecting of the battery. Also, how long does it take for the computer to be reset after disconnecting the battery? Any ideas? Thanks, Chris

Huntaholic · July 31, 2003

My 98 Z71 does the same thing, only it hasnt ever been as low as 14mpg! When you disconnect the battery, the computer has to relearn the settings. Im not sure exactly how many run cycles it has to go thru before it relearns though.

You might go to AutoZone and get them to run the codes in your computer. If it is making that much of a difference you may have some other issues causing the poor mileage.

Race18 · July 31, 2003

I reset my computer when I put in the new fuel pump. I did not notice any gas mileage difference but did notice a performance inprovement. But to answer your question about how long to leave the battery disconnected it takes 35 minutes for the computer to reset. I found out the hard way. Trying to clear the code I started with 10 minutes and went up from there.

cowboy02 · July 31, 2003

So if it has to re-learn something what is it that it's re-learning? How to make your fuel mileage go down? I guess this is more proff that Automakers are in bed with the Oil Industry...........

Chris97K1500 · July 31, 2003

Well I've disconnected the battery again, a couple hours ago. I'm going to go and fill it up and see what happens with the mileage. I'll post back what happens in a couple days. I'm also going to go to Autozone after a few fill ups and see if there are any codes. Thanks, Chris

Huntaholic · July 31, 2003

So if it has to re-learn something what is it that it's re-learning? How to make your fuel mileage go down? I guess this is more proff that Automakers are in bed with the Oil Industry...........

it is relearning fuel parameters, ignition timing, run cycles, etc... while doing this, it will run on what was programmed into it from the factory. Thats why I said he probably should get it scanned if it runs THAT MUCH better after a reset. Did you buy the truck new? If not, it could a code stored in the computer that doesnt set an SES light anymore.

Chris97K1500 · August 1, 2003

No I bought the truck used back in Feb. The engine has a smooth idle, tranny shifts great, nothing out of the ordinary. I will take the truck to AutoZone like you mentioned after I see if the mileage goes up after a reset of the comp. I'll be sure to post back what happens in a week or so. Thanks again, Chris