Replace Oxygen Sensor?

[dantye]

I have the exhaust manifold off of my '81 FI to fix an oil leak around one of the studs. The car was running pretty well and getting 30mpg, so I'm just after the oil leak.

What are the benefits or possible risks of replacing the Oxygen Sensor? I'm pretty sure the old one has more than the recommended 30k limit. Is this what has been causing a red light to turn on on the dash. If so, how do I reset that with a new sensor?

[GeorgeT]

Yes, you need to replace the sensor. A bad sensor will cause the air/fuel ratio to be too rich. To reset the light, look under the dash, just to the right of the steering colum and above the pedals; you will see a black box. There is a small hole that you have stick a small probe into until you hear a "click" (I use an ice pick). This resets the light (in 30,000 miles it will come back on).

[dantye]

Yes, you need to replace the sensor. A bad sensor will cause the air/fuel ratio to be too rich. To reset the light, look under the dash, just to the right of the steering colum and above the pedals; you will see a black box. There is a small hole that you have stick a small probe into until you hear a "click" (I use an ice pick). This resets the light (in 30,000 miles it will come back on).

Thanks! I will order the sensor today.

Could that be all or part of the cause of the rough running I have always experienced until it is warmed up? (Runs fine after that.)

[So Cal Mark]

I don't like replacing parts that are functioning as designed, so I'd test the sensor first. The warning light has nothing to do with the function of the sensor

[dantye]

I don't like replacing parts that are functioning as designed, so I'd test the sensor first. The warning light has nothing to do with the function of the sensor

I understand that the light is just on a counter. Are you suggesting that, if the car was getting 30 mpg, there is a good chance the Oxy sensor is OK? I bought it as a non-runner with 77,777mi. and the sensor was NOT replaced at that time. The car now has over 81K mi. I would be very happy if a new sensor would just fix the cold start rough idle problem.
I can't find any suggested way of testing the sensor that doesn't involve a CO2 meter, and I could probably buy a new sensor for the cost of that. Is there some complexity here I don't understand, or there just a lot of bad NOS sensors out there?

[majicwrench]

The Oxygen sensor will not have anything to do with the rought running cold. The O2 sensor has to be hot before it starts working. As has been said, the light has nothing to do with the functioning of the sensor. To test sensor you need a voltmeter or better yet a lab scope. With engine hot sensor voltage should be varying sine wave tween .1 and .9 volts. But as you surmised, if car getting 30mpg O2 sensor likely fine. The are literally millions of O2 sensors out there with over 100k miles still functioning well.
Keith

[dantye]

Thanks, guys! I think you saved me $50!

[124JOE]

Could that be all or part of the cause of the rough running I have always experienced until it is warmed up? (Runs fine after that.)

hey guys do ya think it might be his cold start vavle starting to go?

[dantye]

Could that be all or part of the cause of the rough running I have always experienced until it is warmed up? (Runs fine after that.)

hey guys do ya think it might be his cold start vavle starting to go?

Last Summer, I replaced both of the hoses on the Aux. Air Valve and that seemed to help some, but it is still a bit gaggy until it reaches op. temp. Will idle OK, but sometimes gags on load.

[So Cal Mark]

test the coolant temp sensor throughout its' range

[wikkid]

And see my post and the link in it HERE for cleaning and testing info for the Aux Air Valve.

[dantye]

And see my post and the link in it HERE for cleaning and testing info for the Aux Air Valve.

Wow! Thanks. That was great info. I have cleaned it out and adjusted it - it was really dirty. One of the first things I had to do after getting this car running was to make a bracket to hold the Aux valve to the engine - it was connected ONLY by the hoses. This was because the DPO had done two tricks: First he broke off one of the bolt-hold flanges on the Valve, Then he stripped the bolt in the engine hole intended to hold the other side down! So it would not rattle around, I made the bracket shown in these photos (from heavy floor pan steel). Now at least it is held down by one bolt.
My question is, does anyone know if this valve should get it's heat via the physical connection to the engine, or just ambient air? If it is important for it to have a solid connection to the engine, then I should probably get some metalized epoxy or the like, and connect the bracket permanently. It will still have only one bolt holding it on - unless I am more successful at removing the broken bolt than the last time I tried!

[wikkid]

My unscientific answer would be that a bimetallic strip is the same technology that is used in a basic home thermostat, so it is therefore fairly sensitive to changes in temperature. Cold is cold, attached to the motor or not. Heat would be transmitted a bit faster to the device if fully attached, but I doubt it would end up making a big difference, and surely none at all once the engine is up to operating temp's.

[GeorgeT]

es does anyone know if this valve should get it's heat via the physical connection to the engine, or just ambient air? If it is important for it to have a solid connection to the engine, then I should probably get some metalized epoxy or the like, and connect the bracket permanently. It will still have only one bolt holding it on - unless I am more successful at removing the broken bolt than the last time I tried!

There should be an electrical connector at the end. The current heats the bimetallic strip.

[dantye]

There should be an electrical connector at the end. The current heats the bimetallic strip.

It's there, and has been connected in operation. I guess I could throw an ohmeter on it to see if the heating element is still there. I have it cleaned out now and it appears to work when I freeze or heat it. It will be a few weeks before everything is back together. Then I will see if it is is getting voltage or if something else is causing my cold start idle problem.

Thanks!