OK, so right now my 305 TBI Firebird is pretty much stock. Won't stay like that for long though

Anyways, I have a new Edelbrock air filter on there...changed out the spark plugs and O2 sensor...yet I'm still getting awful gas mileage? I get maybe 18 or 19 on the highway, and maybe 14 driving it around a largely suburban area.

I know that an F-body with a V8 isn't going to give me stellar gas mileage, but I've heard that TBIs should be getting a little better than that..my friend with a highly modified 305 TBI (new cam and everything) gets 16mpg with a bad transmission...

Any suggestions of what else I should swap out?

 

Maybe run some fuel system cleaner through it, that might help. Not sure what effect that would have on your new O2 sensor though.

 

air filter, spark plugs and o2's and you got that good of gas mileage? I'm jealous! my carbed 305 got 14 after a full tune-up and was running smooth like-new.

You should do distributor cap, rotor, spark plug wires, oil/filter. Also, then complain about your gas mileage

 

Ease off the loud pedal.

 

loud pedal LMAO! Never heard it called that before.

 

Heh, well I have fuel injection, so I'm supposed to get better mileage than a carbed car...

I did spark plug wires (along with the spark plugs) and oil filter...my oil levels seem pretty good...didn't do distributor cap and rotor though...

But what's weird is that even after I did the spark plugs, wires, air filter, O2 sensor, etc...I didn't even see any increase at all in gas mileage? I figured with the air filter I'd pick up at least 1-2mpg.

 

your coolant temperature sensor could be going bad, or you could have a leaky injector or two.

Or your lead foot gets in the way

 

maybe your friends car is geared for bettter milage. My friends Iroc with a 350TPI has 2.73 final drive and my firebird with a 2.8 has 3.42 final drive and I got only marginaly better than his because I have a smaller engine, so it needed more gearing to accelerate quicker where as his didnt cause it was faster from the fatory.

 

Make sure your converter is not clogged, inspect your cap and rotor, stick a timing light on it. If you have many miles on the engine your timing chain has stretched, if nobody reset the timing EVER you could be running a few degrees retarded which will hurt your fuel economy.

 

My TBI car will avg. 22 MPG and get 28-31 on the hwy., but it's a 5-speed, make sure your timing is set correctly or even a few degrees advanced seems to make more power than the stock 0 setting.