Fredbird

I know gas mileage is not a big concern, however mine has dropped somewhat dramatically since replacing the injectors with 22lb. Bosch III injectors.

I used to get in the mid 20's on the highway and mid teens in the city. Now I'm getting in the mid teens on the highway and single digits to lower 10's in the city. (this is without jackrabbit starts/stops or hard accelleration.)

The car seems to run great and has no codes at the moment.

I just recently replaced:

The fuel regulator because it had holes.

EGR valve because I was getting a code 32

MAT sensor because I was getting a code about that.

Injectors... As I said, because I was in the neighborhood and still had the original stock injectors.

And finally the thermistat to a lower temp. because I live in San Antonio.

I have repeatedly checked all my fuel rail connections, regulator, and injectors for leaks.

Car does not "seem" to be running rich, yet I am going through gas much faster now.

aklim

What was in it prior?

How did you calculate the mpg? By hand or the meter?

Klondike

Noticed the same when I changed mine. It's just the dash meter. I keep close track of my mileage on every tank; calculated miles /gal's. Somehow the new injectors fool the flow meter into thinking it's using more gas than it actually is. The car actually gets better mileage than the dash meter tells me now. My mileage went up about .3 to .5 mpg when I put fresh Ox sensors and did the Bosch III's from Jon at FIC. but the dash reading went the other way for some reason!

GKK

My 91 Vette is getting 18.3 mpg city/hiway combined with the 22lb Bosch III's.

Something is not right with your 91. I would install the recommended 195* thermostat since the engine might not be getting to closed loop and will use more fuel.

Also, do a complete tune up including O2 sensor, oil, oil filter, plugs, wires, cap, rotor, air, filter, fuel filter, check tire pressure, check fuel pressure, check timing, change coolant and use the recommended Premium Fuel since the computer will retard engine timing to prevent engine knock if Regular fuel is used, reducing engine power too.

You can also, try disconnecting the battery for 30 seconds to reset the computer so, it can relearn the new injectors. Some people say this should be done when Bosch III's are installed.

Your gas mileage should significantly improve after this tune up.

GREGGPENN

This is a dupe of thread posted in the C4Tech forum!

And, the one in the tech forum has more info going on -- with participation from FIC.


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