LEAN on both banks

[Schurkey]

does the LEAN indicator in the EngineData mean it's running lean?
If not, then what's the purpose for it?

IF (big IF) the sensors are reliable, AND the engine is running properly, lean means lean.

As I've said multiple times, misfire creates a situation where the O2 sensors report FALSE lean, and disconnecting them entirely means the computer is not getting proper signal from the sensors, so it has no idea what's going on. The total lack of sensor voltage would indicate extreme leanness.

IF things were working right, the O2 sensors would correctly report the oxygen content of the exhaust, which is ASSUMED to measure the quality of combustion--rich or lean varies the exhaust oxygen. However, it's an OXYGEN sensor not a carbon monoxide sensor or a hydrocarbon sensor. It does not measure mixture strength directly.

 

[cadman777]

Thanks for that explanation Schurkey.
Makes sense.
So the PCM needs the fore O2 sensors to make a mixture.
But if there aren't any O2 signals going to the PCM, then won't the PCM just use 'limp-in-mode' values?

 

[drifterwanb666]

Thanks for that explanation Schurkey.
Makes sense.
So the PCM needs the fore O2 sensors to make a mixture.
But if there aren't any O2 signals going to the PCM, then won't the PCM just use 'limp-in-mode' values?

if i remember right, (from experience) if the PCM receives no O2 sensor data it stays in warm up mode, since the PCM cannot read what the exhaust is doing itll stay in closed loop. warm up adjusts the fuel mixture rich to help the engine warm up faster, and i belive timing is adjusted also. the computer has preset parameters for this, i cant say what they are.

 

[Schurkey]

since the PCM cannot read what the exhaust is doing itll stay in closed OPEN loop.

FIFY.

 

[cadman777]

Yes, I notied that it was in OpenLoop since disconnecting the O2 sensors.

 

[yevgenievich]

Computer will not know lean or rich without o2 sensors. It is probably just saying that there are no sensor signal essentially

 

[SableSlayer]

I chased all this on my 5.7. I was watching the fuel trims spike at idle and misfires under load. It ended up being the lower intake gasket which had been changed some years prior. Upon removing the intake manifold if found that one of the bolts on bank 2 was missing and the other there were loose. The gasket had collapsed in on itself causing an internal vacuum leak that wouldn't show up with a smoke test.

 

[phantom 309]

i was under the impression that a vac leak will cause the O2's to dump fuel to compensate,. Have you run the truck in speed density?

 

[Schurkey]

i was under the impression that a vac leak will cause the O2's to dump fuel to compensate,. Have you run the truck in speed density?

The O2 sensors will read the resulting O2 content of the exhaust. I'd expect to see the fuel trims go to rich-command especially at idle, along with the IAC closing up to keep the idle speed appropriate.

But if the misfires get bad enough, the idle speed drops, and then the IAC has to open again, and the fuel trims get REALLY rich-command.

 

[cadman777]

I chased all this on my 5.7. I was watching the fuel trims spike at idle and misfires under load. It ended up being the lower intake gasket which had been changed some years prior. Upon removing the intake manifold if found that one of the bolts on bank 2 was missing and the other there were loose. The gasket had collapsed in on itself causing an internal vacuum leak that wouldn't show up with a smoke test.

Thanks for this testimony.
I am hoping that's not the case with this one.
Just took th plugs out and changed them today.
The old plugs that I cleaned were looking very good.
No oil, no rich fouling, but a bit of signs of fuel additive (he burns high test in it).
With the plugs changed it now runs REAL NICE!
Tomorrow I'll change the two O2 sensors.
They are welded into the bungs.
So time to break-out the trusty Inductor.
That thing has saved my life many times over!
After that I'll get some Data to share.
Hopefully that'll cure it.