Update on my gas problems

Chris97K1500 · August 8, 2003

After resetting the computer on my truck following my bodylift I got almost 19mpg. A week later I was back down to 13-14mpg. I took the advice of some people here and disconnected the battery to see if it did it again, yes it did. It went right back up to 20mpg this time. Then today after filling it up, back down to 13mpg! Took it to Autozone to check for any codes, none. Hooked it up, said it was linking, then said passed, no codes. I ask the Autozone guy and he mentioned it could be an O2 sensor with a bad connection, that wouldn't give a code unless it is no longer working. I don't know what to do about this. The only thing I could think of would be fuel filter. But would it make a difference after disconnecting the computer? I also have been noticing that the inside of my exhaust tailpipe is coated black, I assume carbon. It doesn't smoke, but could it be running rich and not burning the gas properly after the computer adjusts? Could my timing be off? Any advice? Thanks, Chris

Shaners · August 8, 2003

I can't imagine how a body lift would effect milage. If anything it should get a little worse!!!

I wonder if when you lifted it, that you might have knocked a wire loose somewhere...

Chris97K1500 · August 8, 2003

Thanks for the reply Shaners! I went over everything about 3 times looking for something disconnected or frayed, nothing. The only thing I can think of is that after disconnecting the battery for 10 hours while doing the lift, the computer reset itself to factory specs. Then over time adjusted to whatever is wrong with my truck. Is 13-14mpg resonable on this truck? Chris

Wingnut · August 8, 2003

Just out of idle curiosity, did you adjust your computer for those 33s?

Chris97K1500 · August 8, 2003

Nope I didn't. The stock 265/75 were 31.7" tall and these 33's are actually 32.4. Would that make a huge difference?

Shaners · August 8, 2003

The bigger tires would cause you to record less miles than actually traveled, therefore if you used your tripmeter to calculate your MPG's, you would show worse fuel milage than what you actually got.

I fugured going from 245's to 265's on my truck threw my odometer off by about 3% .

Chris97K1500 · August 8, 2003

I've taken all that into consideration. Whatever my mileage I take about 3% of it and add to it. At 300 miles I've gone about 310 actual miles. How could I tell if my timing was off, or if I'm running rich/lean? thanx, Chris

bigtruck21 · August 12, 2003

for timing, you need a timing gun. some people claim they can do it by ear but i don't know. For rich/lean pull the plugs. If they are white they are too hot and lean... if black and carboned they are too rich. that or get a gas analyzer.

Huntaholic · August 12, 2003

Welcome to the world of OBDII and the vortec engine! Sounds like yours is doing EXACTLY what mine has done for years! I gave up chasing it down, now I just disconect the battery every so often to reset it. I do wish SOMEONE would find out why they do this!

frdfandc · August 12, 2003

Hooked it up, said it was linking, then said passed, no codes. I ask the Autozone guy and he mentioned it could be an O2 sensor with a bad connection, that wouldn't give a code unless it is no longer working.

Actually, the guy at Autozone is a moron. If you had a poor 02 sensor connection, the computer would either sense a rich or lean condition because the 02 sensor tells the computer how the engine is burning the fuel/air mixture. Therefore a code will set, but probably not telling you exactly what is wrong.