running rich
running rich my younger brother has a 98 camaro Z28. his mods are pacesetter headers ORY pipe (no cats) magnaflow catback, gears, O2 sims, SLP flopac. he has pretty much a stock tune. well he got a SES light. bank 1 sensor 1. so a O2 sensor went bad. its since been replaced and the code cleared. now for some reason, its been running rich.... when he first jumps on the throttle, he puffs black smoke, at high rpm shifts, he even shoots a flame out of the exhaust. he says now his gas milage has went downhill. what could be happening here? 
TECH Regular
Joined: Mar 2007
Posts: 455
Likes: 0
Obviously the vehicle is running rich from the black smoke.You need to have the vehicle hooked up to a scan tool to see what is going on.There is a good chance it has something to do with removing your egr valve though.One other thing make sure you do not have a burned spark plug wire or something simple.A misfiring cylinder will cause the O2 sensor to read lean .4v and below from the extra unburned oxygen going out the exhaust.The ECU will compensate by riching the air/fuel mixture by lengthening the pulse width of the fuel injectors.This will cause the vehicle to be running too rich.If you are not sure how to properly diagnose modern vehicles with OBDII then you are best off to take it to a good auto tech who can.
i remember when my O2 wire got pinched and severed. the car went into a safe mode, dumping all kinds of fuel into one side of the motor to keep it from running too lean, the car was still driveable, but it reeked of fuel and gas milage was super bad. could this be the problem?
