General O2 Sensor help needed

[extremedsm91]

I have no o2 volts??? I have tried 3 different o2 sensors and a different ecu. No change. From my understanding there is 4 wires, one red and black for the heated part of the o2 sensor and the other black is a ground and the white is signal to the ecu. I have 12.x volts to the red wire and the two blacks have good grounds. A 1g dsm o2 sensor reads 0-1v, where does the 1v power come from to send to the ecu? I have tested the wire right by the o2 plug and still get nothing. What ever is wrong here is messing other things up. I really need to get this fixed.

 

[steve]

A 1g dsm o2 sensor reads 0-1v, where does the 1v power come from to send to the ecu? I have tested the wire right by the o2 plug and still get nothing. What ever is wrong here is messing other things up.

The O2 sensor generates the voltage from the reaction once the sensor heats up.

Steve

 

[extremedsm91]

Then what is the problem? I have tried 3 different o2 sensors and I am getting nothing. The car has to be running really rich. My eyes are burning really bad when sitting in the garage with the car running.............

 

[steve]

I have no idea what wrong. I'd go back and make sure that the white wire is good from the O2 connector all the way to pin 4 on the ECU and not grounded. I have seen people blow up the ECU circuits for the O2 sensor by miswiring the sensor.

Also make sure you don't have any leaks in the exhaust from the head to the O2 housing that could be sucking air into the exhaust before the sensor.

Are all three sensors new?

Steve

 

[extremedsm91]

I have checked the wire allready. All the wires have tested out fine. All of the o2 sensors are used. I have about 20 o2 sensors here and just tried one more for the hell of it and nothing. I get .1 volt steady. What makes an air/fuel guage cycle? It just stays dead lean and same thing on my dsmlink. I am going nuts here.

 

[steve]

Just to make sure you are running the car and waiting for the O2 to heat up, correct?

Like I said, I've seen the ECU O2 circuit get fried by miswiring the sensor. So if all else fails try one of a car that is working.

Steve

 

[extremedsm91]

I have been logging it on dsm link for who knows how long. Car is a full temp. Also tried a different ecu. I am stumped..................

 

[steve]

You can double check the sensor by heating it with a propane torch and measuring the output voltage along the lines of the last section in this link.
http://www.gnttype.org/techarea/ecmsensors/O2sensors.html
http://www.napaechlin.com/web_app/TechTips/TechPage.aspx?ID=19

Since out sensors have a connector for the ground you would connect the DVM to it rather than the case.

How did you check the wires for the sensor output and sensor ground?

Steve

 

[cdct99]

Check your LTFT lo and hi in DSMLink. When these trims are pegged (-12.5 or 12.5) the ECU will simply leave the LTFT at that value and the o2's will not cycle. You could actually be running that lean at idle. Also, unless this car is stock, filling out your profile and posting a log would help.

Steve

 

[extremedsm91]

I think I may have figured it out. Will keep updated. Thanks for the ideas.

 

[tom04841]

I am having a similar problem, but my o2 volts are at .92 and hold there unless i give it gas. Then it will fluctuate and go bad to .92v and stay there. I have checked for leaks. I have checked the voltage at the o2 connecton under the hood and at the ecu....same thing. What gives?

 

[steve]

I am having a similar problem.
My o2 volts are at .92 and hold there unless i give it gas. Then it will fluctuate and go back to .92v and stay there. What gives?

You have a completely different problem. I usually see that when people are too rich at idle for the ECU to go into closed loop, allthough there are other sensors that will keep the ECU from going closed loop too. If you have installed larger injectors I'd say you need to lean it out more at idle but your profile says your waiting on injectors, so it sounds more like FPR overrun. What kind of AFPR are you using and what is your base fuel pressure?

Steve

 

[tom04841]

i haven't installed the walbro yet. I am still on a stock fuel system

 

[steve]

Is the car fully up to temp when you check it? '90 don't go into closed loop until the engine coolant temp is above like 120F. I forget the exact point but it's not like '91+ cars that go closed loop at 86F.

What do your fuel trims look like?
Did you swap the MT Turbo FPR in when you made it a turbo?

Steve

 

[tom04841]

yes, that is after cruising for 10 minutes.

I don't have a logger to check my trims....laptop won't work with a passive cable, and my attempt at making an active cable failed.

And yes, when i converted to turbo, i swapped the whole rail, injectors and fpr with the one from the parts car

The problem started after i did the conversion.