SOLVED: Code 41 O2 sensor issue.

[A4LD_Nghtme]

Where is the computer located? Passenger wall under glove box? I can get that done!

also, I did a smoke test. Was wondering if smoke should leak from oil cap and bottom of air cleaner box? Air cleaner box has two holes in bottom of it that I assume are for moisture to escape but not sure. Other than that I don't see smoke coming from anywhere else so I think that confirms vac leak.
I also did a vac guage test and was getting steady needle 17-18 in hg when first started back up after warm, then the idle started going haywire and it drop to around 15 in hg and the needle was extremely unsteady. Maybe I have a clogged injector even though they are basically brand new accels

 

[A4LD_Nghtme]

Where is the computer located? Passenger wall under glove box? I can get that done!

also, I did a smoke test. Was wondering if smoke should leak from oil cap and bottom of air cleaner box? Air cleaner box has two holes in bottom of it that I assume are for moisture to escape but not sure. Other than that I don't see smoke coming from anywhere else so I think that confirms vac leak.
I also did a vac guage test and was getting steady needle 17-18 in hg when first started back up after warm, then the idle started going haywire and it drop to around 15 in hg and the needle was extremely unsteady. Maybe I have a clogged injector even though they are basically brand new accels

I'm going to be replacing the fuel filter today on the off chance seafoam knocked enough stuff loose to clog it. I tested fuel pressure and got between 38-40 psi after grounding pump. So pump is good. 3 minute leakdown sat at 40 psi so check valve is good. With engine running I tested FPR by plugging its vac line and read 42 psi plugged and plugged in to fpr it was about 35 psi. I tested under rev with line plugged and it remained at 42psi. Fpr connected during rev had about a 5 psi jump and then dropped back to 35psi.

After all this I'm pretty certain my pump and fpr are fine

I just hate that thing will run great for about 10 minutes until fully warmed and then become sluggish and CEL comes on. If fuel filter doesn't fix this it's heading to the shop Monday for a diagnosis of all that's occurring so I can check a bunch off my list and get to thing that are less of an issue

 

[rusty ol ranger]

I'm going to be replacing the fuel filter today on the off chance seafoam knocked enough stuff loose to clog it. I tested fuel pressure and got between 38-40 psi after grounding pump. So pump is good. 3 minute leakdown sat at 40 psi so check valve is good. With engine running I tested FPR by plugging its vac line and read 42 psi plugged and plugged in to fpr it was about 35 psi. I tested under rev with line plugged and it remained at 42psi. Fpr connected during rev had about a 5 psi jump and then dropped back to 35psi.

After all this I'm pretty certain my pump and fpr are fine

I just hate that thing will run great for about 10 minutes until fully warmed and then become sluggish and CEL comes on. If fuel filter doesn't fix this it's heading to the shop Monday for a diagnosis of all that's occurring so I can check a bunch off my list and get to thing that are less of an issue

It starts running like shit after 10 min cause thE ECM ignores the O2 untill the engine is at temp.

I think you might just have a bad sensor and/or wireing

 

[RonD]

Two Bridges Calif is at 6,000ft elevation?

Amazed you got 17-18" of Vacuum at that elevation

Engine Computers have two basic modes of operation
Open Loop, used at cold start along with Choke Mode, uses air/fuel mix tables in memory, no "on the fly" calculations based on sensor and O2 feed back

Closed Loop, uses all sensors and calculates air/fuel mix "on the fly"
Engine coolant must be above 150degF for Closed Loop and O2 sensor needs to be heated above 600degF(its why O2s have heaters inside)

Your problem seems to occur in Closed Loop, so could be a sensor issue or computer issue
I wouldn't think Vacuum leak since idle doesn't stay high after warm up

MAF sensor is a main sensor that WEIGHS the incoming air, i.e. MASS air flow(MAF), MASS is weight
Engine computer already knows how much air is flowing in at any RPM, engine size is in liters, so 2.9liter engine will pull in 2.9liters of air every 2 RPM at WOT(wide open throttle) so at 1,500rpm its just MATH to get air flow in liters, and thats what computers are good at, MATH

What computer doesn't know is the WEIGHT of that air
Any Gasoline engine uses 14.7/1 air/fuel ratio, this is a WEIGHT ratio
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline

"Hot air rises", because its LIGHTER than cooler air, its how Hot Air Balloon can fly
So cooler air is denser, heavier than warm air, that's how Cold Air intakes work for better power, the cooler the incoming air the more gasoline you can add to it so the more power you get

Air gets lighter, less dense, as elevation gets higher, at 6,000ft its very light, MAF needs to compensate for that, as does the computer
There is also an IAT(intake air temp) sensor
Between the two the air weight will be very accurate

In the old days with MAP(manifold absolute pressure) sensors, people would drive up into the mountains and engine would start to run poorly, if they stopped, turned off the key, then restarted the engine it would run better, because they needed to reset MAP for higher elevation
MAF sensor doesn't have that issue, it can compensate for cooler air, warmer air, lower elevation and higher elevation "on the fly", because its "weighing the air" as it passes by the sensor
But................it only weights 10-15% of the air passing thru the sensor, lol, so any small errors are multiplied at least 10 times for computer

 

[A4LD_Nghtme]

So I have an update. It's an odd one. Before this check engine light came about, I had refilled my tank(23 gallons) and added 16oz of High mileage Seafoam and 4oz of Marvel Mystery oil. I assumed this was OK given 1-2 oz per gallon of seafoam is recommended and 4oz of mmo treats 10 gallons. This would put me around 18-26 gallons of treatment. I drove about 70-80 miles before cel came on. I've used fuel system cleaner many times with no issue but not in high concentrations nor in conjunction with MMO, so I was testing it out plus I needed to use up what I had left.

Anyways, I'm not saying this caused the lean issue because I don't know, but the other day I drove my usual 15 miles to Walmart maxing out at 45-50 mph. The cel did end up coming on at this time and the Bii lost power. I left wallyworld(when car is off, cel does not come back on after restart till driving a few miles), and hit the highway and got her up to 75mph for the first time in probably 8 or more months and drove about 3 miles to my exit.

After this, the cel has not returned and the Bii has been running much better minus an idle that is a tad rough. I have traveled over 100 miles in this time and NO CEL.

Is it possible that the products I used did their job cleaning up the engine but clogged something up to cause this Lean Code 41? Also, is it possible that a good old Italian tune up helped cure this issue? Because I am absolutely stumped but would like to think this has been solved; at least for now.