I recently rebuilt my 92 Si and ever since it runs so rich I can barely afford to put gas in it! Well the ecu threw a code for the O2 sensor and i changed that out and it got a lil better It also threw a code for the EGR valve before I rebuilt it but I got an EGR blocking plate. but even if I go into town on a full tank, I come back at almost half! This is ridiculous. I checked to see if anything was leaking, turned the fuel pressure way down checked the ignition timing and....Nothing. Still rich. I know the ECU ultimately controls how much fuel the injectors spray, Could it be the ecu? Im out of ideas does anybody have this problem?

 

I would think it's the airflow sensor (map sensor, mas sensor, whatever airlfow sensor you have). If the airflow sensor tells the ecu it's getting more air into the engine the ecu will automatically inject more fuel. Maybe you have a vacuum leak or some sort of air leak...Is it idling weird?
I can be your TPS, throttle position sensor. If you messed with your throttle body, then that could be one of the things that are messing with your MPG. If the TPS tells the ecu that the throttle plate in the throttle body is open then the ecu will inject more fuel into the engine, reducing mpg obviously.
I know that the EGR would cause you to lose mpg if the valve is faulty or stuck, but I forget how it causes this.


Modified by Dulluthkid_19 at 4:50 PM 1/2/2005