OK when i start my car up cold i can seriously sit there for like 5 to 10 minutes and watch it go from fiull tank to a little over 3/4s cuz that happend this morning. What would cause this i know i have bad 02 sensors yes plural i have 3 bad ones. i just cleaned the air filter. my buddy said it could be the senders for the fuel. what do you guys think

 

Holy crap that's terrible. It may just be the floating gas guage that all F-bodies havethough. My needle floats every time I slow down or speed up.

 

yeah its just the guage floating. Mine does that too i dont worry too much about it until i get around 1/4 tank and refill.

 

even when im sitting still at idle it will do that? cuz i used to have a chevy truck that did that and when i hit the breaks or gas it doesnt move like everytime i restart the car the gas tank reader says either higher or lower than it actually did when i turned it off.

 

well its not the most accurate way to read the gas level. But when you start the car the motion of the car and everything flowing could cause your gas to shift in the tank giving the floater a hard time.

 

My 96 Z is getting about 5 m.p.g. right now, I have just found out my check engine light is out. When this goes out or isnt working properly it messes with your computer, and i was told puts your car in a mode called "limp" mode. This doesnt let the car idle like its suppost to, so make sure your check enginle light comes on when you start your car.

 

it does come on but it is for the 02 sensors i have a thing that reads what it is and im gonna order the sensors this week so hopefyully it helps a little i hurd 02 sensors help mpg a little bit well bad ones decrease the gas mileage

 

The O2 sensors will affect gas milage, but it's not going to drop that much at idle just from O2 sensors. Plus, for the first couple of minutes the car runs in "open loop" mode, where it doesn't even take mixture data from the O2 sensors. My bet is the O2 sensor(s) are setting off the SES light because they have bad heaters, which means they're giving faulty data and the car isn't running quite like it should, but it's not going to make that big of a difference. I'm agreeing with other people in saying the float is probably a bit off, I know my gas guage is horrible about that, and from what I've heard it's about the same on all F-bodies, if not most GM vehicles in general.