View Full Version : Need help, O2 sensor is messed up

04-10-2004, 05:22 AM
Hey guys, okay I'm at a loss here, I just replaced my fuel injectors with larger ones, 19.6 lb/hr and after replacing them the check engine light came on. I figured it was just a fluke so I reset it and it stayed off for a little while, then after driving about 10 min the check engine light came back on again. The code its giving is the O2 sensor. I reset it a couple more times, and same thing, after about 10 min of driving it comes back on....what gives?:confused: I didn't touch anything to do with the O2 sensor, and since I put the new injectors in the car has been running amazingly, better than it has in a while. So what could be causing this? the O2 sensor was just replaced about 30,000km ago. I don't understand why new injectors would cause the O2 sensor to fail....

04-10-2004, 10:26 AM
maybe your mods dont require more fuel...probably to much unburned gas on the sensor....

04-10-2004, 04:28 PM
They probably don't but I would have thought that the computer would compensate by leaning out the mixture. The reason I put the larger injectors in is because my old injectors needed replacing anyway, and at some point in the future I will be going forced induction, so I figured now would be a good time to upgrade. But shouldn't the ECU "relearn" the new injectors?

04-11-2004, 12:26 AM
no it shouldnt - they arent designed t odo that otherwise we would have wonderful programmable computers in out e30 and we could do what we want, but thats not what we have.

The computer is designed to read a cetain range of oxygen/fuel/emmision levels coming out of the exhaust - your've put bigger injectors in, hence more fuel, if your've got a good air flow going to your engine, your gonna get more power, just as you have said.

Its not a broken Oxogen sensor - the computer just cant understand the readings coming out of it. capish?

04-11-2004, 06:53 AM
I understand that yes, but it just dosn't make sense...because the O2 sensor is there to read the mixture...so if there is too much fuel, ie the mixture is too rich, why would the ECU not just lean out the mixture? Its not like I put 30lb injectors in its just a small increase from 13.5lb to 19lb...it should be able to handle that....