I got a question about gas milage. i got a 91 camaro with a 305tbi and i get really bad gas milage and im talking like 12mpg city 15mpg highway. i took the throttle body off and got it professionally cleaned, hollowed out the cat. convertor, put a k&n on it. what else could i do or what could be the problem?

 

o2 sensor.

 

TONS of stuff can effent your mileage.
Here is SOME stuff to do/check:

Easy stuff first:
-Full tune up (timing set right? Get New: cap, rotor, wires, plugs, pcv, fuel filter, air filter, ect...)
-Tire pressure in spec and consistant?
-Fuel pressure with and without vac hose connected to FPR in spec?
-TPS and IAC adjusted properly?
-TV cable adjusted correctly?
-Are you running the correct octane gas, have you tried different ones?

Tricky Stuff:
-Vac leaks?
-sensors in spec, there are alot of these and they're almost all very important (need a scan tool 4 most)?
-Exhaust leak at engine (this can skew ur O2 readings and kill ur mileage)?
-Injectors clean and consistant?
-Engine compresion in spec and consistant?
-Tranny slipping?
-Overheating?
-Fuel leaks (don't laugh until you checked the whole system at pressure)
-Ect...

Start with the easy stuff first to save yourself time, money and busted knuckles. To get more info on any of these or how to check/do them, search, search, search.



:rockon:

 

You probably have a problem, and it's probably one of the above listed... but one thing you could do is get some headers, they can make a big improvement... probably up to 3 MPG on a well tuned engine... of course the added free flow and nice sound might make you stomp on it more and thus negate the increase.

 

Just curious, what are good gas mileage figures for these cars? A 305 TPI 5-speed's gotta be well into the 20s on the highway...

 

1990 305 TPI 5-speed 3.08 rear, my best hwy. MPG was 25. My RS w/ 305 TBI auto trans. and 2.77 rear once got 29 MPG!

Around town, I average 15-18 MPG in both.