Quote Originally Posted by demetriuslopez View Post
Hey guys! SES light came one about 2 hours ago. Got it scanned and P0300 & P0420 codes came up. About a month ago my car was running horrible; engine was hesitating, very little power, and stuttered. No SES at the time. Changed the MAF, Plugs and wires, fuel pump and all did nothing to help. LAst weekend i gutted the cat and rigged my o2 sensors with two defoulers. Car ran better then it ever has before. Power was awesome and got to 95 mph with ease, keep in mind i had never gotten past 75 in the last year. About 150 miles after i gutted the cat the codes above came on. Also, i was getting 12 miles/gallon at my last fill up. Any suggestions to what my problem is?
Hey there, have you changed the fuel filter? If so, do a pressure check on the fuel system. I hook pressure gauge to fuel rail and then tape dial to the windshield so you can see while you drive around the block, should not dip below 25-30 psi. Listen to the fuel injectors if you can, all should sound alike. Fuel delivery is based on about 4 sensors til the car gets to normal operating temperature, the it is solely based on the o2 sensor, which might explain the poor fuel milage. I'd put some sort of cat back on if it were me. Maybe that might help