Fueling/ BLM question?

[Julian 537]

Bill,

I am trying to log data on Dash's Scout. Something odd is happening though. When we are logging data, the BLM's are not changing and the O2 sensor voltage stays at .443.

At first we were getting an error on the O2 sensor, so we put a new one on. The O2 sensor error went away, but we are still only getting .443 voltage and the BLM's stay at 128. They do not change at all.

We swapped computers and still got the same information. .443 volts on the O2 sensor and the BLM's never changed from 128.

All the other ALDL data is coming through fine. TPS voltage, TPS percent, temp, RPM, etc.

Any ideas?

Thanks in Advance.

[Bill usn-1]

Where is the O2 mounted?
Did he put headers on it?
If the O2 is a ways away then he will need to go with a 3 or 4 wire heated O2.

The other thing to look at is the O2 ground and the Sensor grounds.
The O2 gnd is normally tan IIRC.

When I left TX he still didn't have all the wiring tailored and loomed.
Is it still the same?

I think Tommy helped him.

[Julian 537]

Th O2 is mounted in the large collector tube of the drivers side header. He is using a single wire GM sensor.

His wiring is semi tailored and it is all loomed. I did a continuity test on the O2 sensor wire, from the sensor to the D7 pin at the computer to make sure it was not shorted or grounded out.

I forgot to mention, he is getting a "Lean" flag.

I am not sure why his single wire O2 sensor is not working properly? I ran a single wire O2 sensor in my header collector pipe. It was fine. I will see if he wants to spend the time to put a heated one in his scout.

Could this also mean his computer is staying in "Open loop"? This would explain, why the BLM's are staying at 128?

[Dash Matthys]

Bill you would be proud of me. I cleaned up the wires and loomed everything when I did the 392 swap. I have a feeling that Julian would like for it to look better though!
I did add headers so I guess the new O2 sensor is in my future.

[Bill usn-1]

I am proud of you Dash.
How did I know you had headers!!

I didn't think about the 392 swap tho.

[Dash Matthys]

Originally Posted by Bill usn-1

I am proud of you Dash.
How did I know you had headers!!

I didn't think about the 392 swap tho.

MORE POWER!!

[Bill usn-1]

Originally Posted by Julian 537

Th O2 is mounted in the large collector tube of the drivers side header. He is using a single wire GM sensor.

His wiring is semi tailored and it is all loomed. I did a continuity test on the O2 sensor wire, from the sensor to the D7 pin at the computer to make sure it was not shorted or grounded out.

I forgot to mention, he is getting a "Lean" flag.

I am not sure why his single wire O2 sensor is not working properly? I ran a single wire O2 sensor in my header collector pipe. It was fine. I will see if he wants to spend the time to put a heated one in his scout.

Could this also mean his computer is staying in "Open loop"? This would explain, why the BLM's are staying at 128?

What about the wire i asked about?
the tan D6 O2 sensor ground?
If you were reading .443 on the O2 then that told me D7 was probably fine.

128 is a commanded fuel rate. Normally when the ecm can't figure out what the fuel should actually be based on the inputs.

You need to pull the chip and verify no legs have been bent/folded.

You "can" run a 1 wire O2 with headers. I'm sure it's all explained in the FAQ's.
The problem is the O2 will cool down everytime it idles and go back to open loop.
Not always a bad thing if Dash also installed a cam when he dropped in the 392 and headers.


If he has a cam then the chip should be set up for open loop idle anyways.

When tuning do not over lean the fuel table.
If you shoot for 128 using the wide table you will lean it out especially at idle.
I always go to the rich side and let the computer do the tweaking.
There is a big change from cool winter air to thin summer Tx air.

You'll know when the idle starts to roll up and down.


So stay around 126.

[Dash Matthys]

I just have a stock cam.

[Julian 537]

I did not check the Tan D6 O2 ground wire. That should be pretty easy to verify if it is grounded. We will have to check that and get back to you.

[Julian 537]

Thanks again for your help Bill.

It was D6 the tan wire. Dash did not have it grounded.
I have not had a chance to log any data yet, but it stopped his SES light from coming on. I assume it fixed his lean flag and it is now entering closed loop. I will get back to you after I log data.