I just don't get it. My '94 GSR gets awful gas mileage. If I don't drive with a lead foot, I'm still lucky to get 23 mpg! When I first got the car I was getting 17-18 mpg, so I've gotten it to go up a bit. I've replaced the plugs with NGK iridiums, put on new NGK wires, and run fuel system/injector cleaner. I've also swapped out the ECU for a stock one so that now I'm not running as rich (no two-tone back bumper anymore), made sure my tire pressure was good, ran a compression test (and got decent numbers), and my air filter seems to be in ok shape, although I will probably be replacing it soon. What else can I possibly do? I drive quite a bit for school and work, and I am paying like $250 - $300 a month just for gas! Somebody please give me some insight...I feel like just selling the car for another one in better shape or something if I don't figure this out soon. Thanks.

 

What's the mileage?

Cap & Rotor , Fuel filter, PCV valve, Oil change.


Reset your ECU due to fact that you swapped it out. It's possible that the ECU remembers when the car ran rich.

 

do u fill ur tank full every time it gets empty, cuz u know that it is extra load..... and also depends on what ur running?na/turb/supaCharge

 

Did you check his sig?


'94 GSR: Type R Cams/Intake/DC Header/Apexi WS Exhaust/9005 Conversion

Looks NA to me! :chuckles:

 

I replaced the fuel filter about 4 months ago, I do oil changes every 3500 miles, and I've properly reset the ECU. While I haven't done cap and rotor or pcv valve, I don't see how these could account for such a drastic reduction in fuel economy. I usually get about 250ish miles by the time it is on E. Divide this number by what usually is around 11 gallons and you get like 23 mpg. Could a bad thermostat account for such a big drop? I am pretty sure my thermostat isn't working all that well since it usually takes a long time to get past C when it is cool out and the temp gauge will drop back down to nearly C if I am on the highway....Any other ideas?

Oh yeah, could getting a VAFC and tuning it help? I mean, since you can optimize a/f and whatnot. My buddy suggested at least hooking up an air fuel meter to see how it's really running...

 

The oxygen sensor could be one of the causes. Has it ever been replaced?



Drastic reduction, I wouldn't consider that drastic for a 94 GSR. This car averages 25mpg/city driving.

 

Yeah, I just replaced the (one and only) O2 sensor but I am still throwing a code for a heater wire circuit malfunction. I haven't the slightest clue how to fix that though.

 

If you did the ECU reset procedure after installing the new sensor, and you still have a check engine light, it's possible that there's a shorted wire at the ECU side. Troubleshooting O2 sensors codes are a pain and would require a multimeter if you wanted to find out the problem on your own. You would have to measure resistance between connectors on the harness side. That would make sure that it's not the new sensor that's defected. Process of elimination.

You replaced the sensor with a new one and still have the same problem, that's strange. I think it's safe to say that the sensor problem and gas mileage problem are related.

 

Replace the fuel injectors instead of just cleaning them? Or get em professionaly cleaned?

 

I had the same problem with my VTEC sol. Thermostat wasnt getting much past C, then on the highway it would just drop right below the C. I changed it, it was stuck open. gas milege went from ~290 a tank to about 330.