That's ok, I have a photo of it, just checking....

 

Since it was brought up;

ECA Ground Pins; 60, 40 & 20 (49, may be an optional wire), 46, 62, 63.

While you are making continuity checks, if you have the time and desire, suggest these ground paths be verified as well.

 

Code 41 does not mean "bad O2 sensor". Code 41 means the sensor reads a lean mixture all the time. You never know if the O2 sensor is lying or telling the truth. Since you have changed the sensor for a new one, we can assume it's not lying.

You can try the grounding thing and see if it helps. If it doesn't then assume the O2 sensor is working and the engine is running lean. This could be simply a hole in a vacuum hose or a hose that has fallen off, and letting the engine suck too much air by the carb.

How it works; The computer waits till the engine is warmed up fully, and then it goes into what they call "closed loop" mode. What it will do then is signal the carb solenoid to go rich, then looks at the sensor for it to go rich. It then signals the carb to go lean, and then it looks at the O2 sensor to go lean. It does this constantly. In your case the computer signals the carb to go rich, and the O2 sensor is still lean. It tells the carb to go even richer, it is looking at the O2 sensor and it's still lean. It tries for a few minutes to make the sensor go rich, if it can't it gives up and spits out the code 41. Code 42 is the other code you will get, O2 sensor is rich all the time.

 

Additional info; I failed Maryland admissions because of extremely high hydrocarbon reading. Would that happen if the O2 says lean and the computer enriches the mixture?
This is a project that I want to redo correctly, however I am forced to pass emissions test for registration to remain valid. Tailpipe was replaced for safety inspection and now is coated black. The truck is running to rich so I am looking to solve that.

 

You may indeed need to try the ground thing if it's running that rich but the sensor says it's lean. And also test the wiring.

I had a van once that would do this, I would replace the O2 sensor and it would work great for awhile and then it would start running rich, the sensor would say it was lean. Come to find out the engine was burning some oil(I knew it used some) and it would contaminate the sensor and mess it up. I found if I unplugged the sensor wire and just let it lay there, then the computer would ignore the sensor and the tailpipe would quit stinking. I know this is not a long term solution, but you could experiment with it and see what happens. With it disconnected the computer should go to open loop, and use the parameters in the computer memory to run the engine. I wonder if it would pass using these parameters?

 

I am attaching some pictures of my truck. I hope these are helpful, at least you can see what I am talking about

 

I can certainly try that as an option but what would be the long term fix?

 

For me the first step would be to read the voltage directly at the O2 sensor.

To do this you will need a digital volt meter (DVM).

The oxygen sensor generates it own voltage after it warms up. So disconnect the connector about 8 inches from the O2 sensor. Hook the DVM positive lead to the O2 sensor and the negative to a good ground.

Start the engine. You should see a rise in voltage by 2 min.
Max voltage is .9 volts = rich
min voltage is .1 volts = lean
.5 volts is perfect mixture

If it is lean try shutting the choke to raise the voltage.
If it is rich and the choke plate is fully open, you can pull a vacuum hose to add more air (lean) and see if the voltage drops.

Jim

 

Is there a wire connected to the black choke cap on the back side of the carb?

I can not tell from the photo.

The pictures really help, it has been awhile since I have seen one of these trucks as intact (stock) as yours is.

Jim

 

Yes there is a wire going to the choke cap.

 

Dave has some good points as usual;
(Check for vacuum and exhaust leaks and repair prior to testing)

During KOER, Code 41 means lower than expected voltage measured at the ECA. (Interpreted as a lean condition)

The Engine needs to be fully warmed up just prior to KOER test. If the O2 sensor cools down during the test, the O2 sensor may not respond properly.

Other possible causes; O2 sensor failure / Engine running lean / Signal Path failure / Ground Path Failure / ECA failure.

If your engine is always running rich, as you seem to indicate, then the ECA may be receiving a constant low voltage from the O2 sensor.

Since you have a FeedBack Carburetor, (I’m not familiar with) The ECA is is telling the carb to run rich as Dave states.

Another possibility is that you Carburetor is not operating properly causing a rich fuel/air mixture.

If you disconnect the O2 connection you will have 0.0 vdc at Pin 29 and the ECA will interpret as Lean and continue to push your Carb to go rich. If you want to fool the ECA, you have to provide a 0.45 to 0.80 vdc source on the wire. (neither Lean or Rich)

Seeing your photo, the ground may be ok since it is in the Manifold, but check it from the base of the O2 to the battery ground.

 

From your initial text, you received Code 41, replaced your O2 sensor, and still receiving Code 41. Chances are when you test the O2 Sensor it will test ok.

Like JimsRebel/Jim states, choking it some should produce a Rich/higher voltage condition. (0.85 vdc or higher) I’m thinking if your engine is running rich regularly, you will see this higher voltage without choking. According to my manual, this engine is in Rich mode at Hot Idle.

I assume your upstream connector is clean and tight by now. If you receive a 0.85 vdc or higher voltage from the O2, you should verify the same voltage at ECA Pin 29.

Your Feedback Control Solenoid (FCS) controls Rich/Lean mixture at your carburetor, controlled by a signal from the ECA on PIN 58.

During Open Loop, Cold Start-Up, for the first 2 minutes, the ECA puts the FCS in Rich mode, then it switches to Balanced mode, going Rich with Acceleration and Lean with Deceleration. My book states it is in the Rich mode at “Hot Curb Idle”

This solenoid could be stuck in the Rich position, or the ECA is stuck outputting a Rich signal to the FCS. Jim has some experience with these I believe.

(“The Feedback Control Solenoid operates in a rapid ON/OFF way.
Power is applied to the solenoid and disengaged rapidly by electrical pulses. The EEC-IV controls the fuel mixture either lean or rich by how fast or slow the pulses are sent.”)

If your Engine Coolant Temperature (ECT) does not report to the ECA that the engine is warm, the ECA can stay in the Open Loop mode and continue to send a Rich signal to the FCS.

Your Manifold Absolute Pressure (MAP) Sensor input to the ECA can affect the Fuel/Air mixture adjustments the ECA outputs to the FCS.

 

My thinking is if the ECU is giving you a lean code and motor is running rich then the ECU and carb are trying their best to do what is needed.

You need to see what the 02 is doing from the sensor all the way to ECU before digging into the other stuff.
just my .02
Dave - - - -

 

Your Feedback Control Solenoid (FCS) controls Rich/Lean mixture at your carburetor, controlled by a signal from the ECA on PIN 58.


The FCS is normally rich and when the solenoid is energized it goes full lean.

I believe the FCS has a steady 12 supplied to it and is energized by a ground supplied at the computer, as needed to control rich-lean mixture, but this is just from memory and should be checked.

The FCS is bolted on the side of your carb next to the purple tag. It has 2 screws and 2 wires coming out the bottom. You can disconnect the connector and test the FCS by connecting 1 wire to 12v and the other to ground, you should hear it click when it is energized.

If your Engine Coolant Temperature (ECT) does not report to the ECA that the engine is warm, the ECA can stay in the Open Loop mode and continue to send a Rich signal to the FCS.


The Open Loop Mode vs Closed Loop Mode of operation can be checked using a timing light. Open Loop means "fixed timing" without any advance when you rev it up a little. The ETC is near the upper radiator hose on the engine side.

Jim

 

FYI; Carter YFA 1bbl - ???Gary's Garagemahal