BUILD THREAD 84 Hurst Olds - TechG8

[Gonzo1970]

Its as if the sensor is not sending enough voltage and the system is not going into closed loop function as a result.

I checked the bung installation. It is an inch or two rearward of the header collecter, in the head of the exhaust pipe. I looked into the pipe and the sensor is not at all obstructed. I suppose I could have gotten a bad sensor. but twice? I doubt the headers can lose enough heat to make the sensor malfunction.

Is there a way to bench test an O2 sensor?
is there a part number for a heated O2 sensor that works in our cars?

My O2 Bung is Before the Collector.. But have the same issue.

-Gonz

 

[Gonzo1970]

Maybe Ill send it along with the Carb when you rebuild it 🙂

-Gonz

 

[techg8]

yes I have put the engine on the fast idle cam 2500-3000rpm and watched dwell while I choked the carb and made vacuum leaks. no changes in dwell.

The only time the dwell seems to change is as follows:

cold start ~32dwell seems to change to 40 or so once the engine heats up a bit. It does not vary nor respond to idle mixture changes like closed loop should.

The dwell will drop lower at preset throttle position sensor inputs like part throttle and WOT, but it is strictly related to throttle position, not responding to O2 sensor reading.

when I ground the O2 sensor ecm lead, the dwell drops really low like it should.

This in particular makes me want to believe that the ECM is working just fine but it is not seeing the signal it should from the O2 sensor.

 

[techg8]

I am going to recheck the O2 sensor circuit ground for opens or poor ground.

Otherwise I think the heated O2 sensor may be the solution.

Will advise.

 

[fleming442]

Aren't they 1 wire? My only reference is my old 3.8. If so, it grounds to the header...

 

[Gonzo1970]

Aren't they 1 wire? My only reference is my old 3.8. If so, it grounds to the header...

It is.

For a heated, tho... you run a Key On Positive and its own ground.

Basically, it comes with a Pigtail of 3 wires... 1 for ECM, 1 KOP, 1 Ground. (And they're about a hundred bucks... But hey, techg8 will have the extra scratch soon enough when he gets my carb... heh)

-Gonz

 

[techg8]

yes they are one wire, but no the sensor circuit does not ground at the exhaust. That would be a short circuit and would omit the ECM. I was referring to checking the ECM O2 sensor circuit ground.

voltage generated by the O2 sensor runs through the purple wire to the ECM, then back out the light brown wire to the harness ground at the back of the engine block.

 

[techg8]

I found a deal on AMAZON. got an AC Delco 213-3076 heated sensor for $14! its on the way and Ill give it a try at that price.

EDIT:
….and i see that 213-3076 is a WIDEBAND AFR four wire setup that I believe inverts the output. In our cars with a full rich command - low dwell - we should see high (.8) V according to the book. I believe with the four wire style it is the opposite, IE rich exhaust = low V so that WILL NOT WORK for me.

on further research, an AC 25176708 (bosch 13077, AC 213-632, Walker 250-23005)
is a three wire sensor that will work. according to this website, its the right fix for headers.....

Installing a 3-wire Heated Oxygen Sensor --SETHIRDGEN.ORG--

 

[69hurstolds]

Hmm. I see Amazon has them for $40.71 with prime.

You can always send the other one back, or cancel the order if they haven't sent it yet.

One thing about those F-body guys. When they see an issue, there's always someone who comes up with a work around.

 

[69hurstolds]

Found a GM connector on ebay if you need that.

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