so, im working with a tuner to get the duster drivable enough on the efi to take to him.
what we are running into is an issue I cant find.
according to the oxygen sensor, its running dead lean. like pegging itself lean. he said hes never seen it peg that consistently on lean, and wants to keep adding fuel based on that.
according to plug reading and my nose, its dead rich. plugs are black and sooty, exhaust is blue/black, its popping through the enxhaust, and my eyes are watering.
so what can cause this disparity between sensor readings and reality? I want to check everything I can, and find this problem. I don't see or hear any massive exhaust leaks prior to the narrow band o2 sensor, and don't see any evidence of a dead cylinder. oxygen sensor is located on drivers side header collector.
a thought I had, even though its timed properly, is maybe, somehow, its 180 out on timing, but it shouldn't run that smoothly.....
im stumped.
throw everything at me, no matter how far fetched, but give some reason why I need to check it.
Wires reversed on something? Simple answer first.
When you say lean, what voltage?
Sounds to me that your O2 sensor isn't actually alive.
Dead, miswired, or whatever O2 sensor.
Or exhaust leak before the sensor.
I'll have to pull my data when I get home but I don't think I've ever seen it flicker from 450 millivolts
I agree it sounds like an electrical problem on your sensor - bad wiring connection, reversed wires, something. My first reaction is a bad ground on the sensor....?
This is stuff I had not considered please keep it comin guys I'll be checking all this tonight when I get home from the munchkin soccer practice
450mV isn't bad. Steady 450mV is. Unless it's no operating, I've never seen an O2 sensor be steady. Especially around that voltage- as that is the area where the volt to a/f is super steep.
If it's really steady, it's not a leak, it's not a misfire, it's a sensor issue.
An O2 sensor reads oxygen content, NOT fuel. The sensor is reading high oxygen levels in the exhaust, not high AFR (that is a computation).
When the fuel mixture gets so rich that the motor starts misfiring, the missfires contain oxygen that the O2 sensor reads and is interpreted as lean.
Lean the motor out in that area, you are correct to use all your senses when tuning a motor.
Sight, smell, feel, sound, even taste! Dont rely on one indicator.
If you had a multi-gas analizer you would see the HC is high as well as the O2.
bentwrench wrote:
An O2 sensor reads oxygen content, NOT fuel. The sensor is reading high oxygen levels in the exhaust, not high AFR (that is a computation).
When the fuel mixture gets so rich that the motor starts misfiring, the missfires contain oxygen that the O2 sensor reads and is interpreted as lean.
Lean the motor out in that area, you are correct to use all your senses when tuning a motor.
Sight, smell, feel, sound, even taste! Dont rely on one indicator.
If you had a multi-gas analizer you would see the HC is high as well as the O2.
Was just gonna say it could be an ignition problem for the same reason. I learned that one the hard way myself...
Is there any sure-fire way to test the sensor itself to make sure that it is functioning properly it is a standard GM 4 wire oxygen sensor from a mid-90s LT1 Camaro
GameboyRMH wrote:
bentwrench wrote:
An O2 sensor reads oxygen content, NOT fuel. The sensor is reading high oxygen levels in the exhaust, not high AFR (that is a computation).
When the fuel mixture gets so rich that the motor starts misfiring, the missfires contain oxygen that the O2 sensor reads and is interpreted as lean.
Lean the motor out in that area, you are correct to use all your senses when tuning a motor.
Sight, smell, feel, sound, even taste! Dont rely on one indicator.
If you had a multi-gas analizer you would see the HC is high as well as the O2.
Was just gonna say it could be an ignition problem for the same reason. I learned that one the hard way myself...
Except that you are both wrong if the sensor is actually steady. It will move when fuel is burnt on the surface. Yes, it will see a lot of O2, but if it's not reacting, well.
That, and 450mV = .45V, which is roughly stoich in terms of remaining O2. And the signal will never be steady there if it's alive.
You are both assuming a misfire. Before even thinking that, lets make sure the measurement is real.
Dusterbd13 wrote:
Is there any sure-fire way to test the sensor itself to make sure that it is functioning properly it is a standard GM 4 wire oxygen sensor from a mid-90s LT1 Camaro
Take it out, heat with a propane torch. You should be able to see it move doing that, if you put the flame onto the sensor.
BTW, what two wires on the sensor are you monitoring? And what two wires are you applying 12V to for heating?
Gray is signal one white is Switched hot other white is ground black is ground
When doing the blow torch test do I monitor at the ECM or do I do it with a multimeter
I'd check it with a multimeter first to make sure you're getting good signal from the sensor, then check it at the ECM to make sure the signal is getting to the ECM.
Dusterbd13 - so there are two white wires with different functions? How do you know the correct one is connected to the correct circuit? (sorry, never pinned out an O2 senesor)
The only way I knew the way 2 wiring it was by the diagrams given by Al Gore's internet will check continuity at the plug to the sensor and see what we're getting there
ultraclyde wrote:
I'd check it with a multimeter first to make sure you're getting good signal from the sensor, then check it at the ECM to make sure the signal is getting to the ECM.
Dusterbd13 - so there are two white wires with different functions? How do you know the correct one is connected to the correct circuit? (sorry, never pinned out an O2 senesor)
I'm quoting this to repeat the voltmeter check instead of the ECM.
Also- the two white are heat, volts should be checked between signal (black) and ground (gray).
The two white wires are the heater- and should be 12V power and ground to themselves- it does not matter which is which- the heater is just a resistor. DO NOT run 12V to the black or gray wire.
But the black wire will be up to +1V relative to the gray wire.
In reply to alfadriver:
Might also be important to ground the 'signal ground' (as opposed to the 'heater ground') to the SAME ground the ECU uses... Its easy to assume all grounds are the same but sometimes they are not.
Currently I have the heater ground and sensor ground at the same point I'm also not understanding how to do the volt meter test do I pull the sensor completely out but one lead on the signal one lead on the ground and hit with a torch with it laying on the workbench or do I need to add 12 volts into it and then hit it with a torch
Connect the gray wire to the negative/black input to the meter, and the black line to the positive/read input to the meter.
Then torch. It will generate voltage all by itself.
The voltage input is just for the heater. And you are heating it with the propane torch, so that's not needed.
finally had a chance to check the datalogs tonight. either 450.8MV or 0. nothing in between. and over half the open loop time was at 0.
so I guess its time to dig deeper. I'm thinking bad ground or sensor. but its grounded to the same bolt that the rest of the ECM wires are grounded to, and the heater works, which also shares the ground bolt. so maybe bad signal wire? or bad sensor. but definitely a contained sensor problem. I think. right? maybe?
