Lurker finally raises his hand for P0171

[icetherice]

Hi all, first post, glad to be here

I spent a long time lurking this forum and have found a lot of good information here. I finally ran into a problem I need a few opinions on.

Long story short: I built this engine in my garage from the rings up using information that I primarily found here. Runs like a champ. I have been chasing a P0171 for the 3500 miles that this engine has been in service.

Here is the laundry list of things that I have done:

Fuel filter replaced w/ motor

Fuel pressure test - 63psi@850rpm held >60psi doing a 3rd gear pull to 60mph at 3/4 throttle, I think I can rule out a fuel delivery issue.

DPFE test - Voltages from 1.2v - 3.3v within acceptable range and responds to suction/pressure normally, I want to rule this out.

Put muffler putty on the EGR tube in an effort to seal whatever leaks there might be from when I welded the DPFE feed tube back on. It was cracked off when I got it off the old motor.

MAF test - Voltages from .9v - 2v from idle to whatever rpm I happened to be holding the motor at, I don't actually know, but the voltage rose and fell smoothly, I want to rule that out.

IAC - Replaced it on a whim due to the idle kind of hunting..no change

Listened to all injectors with stethescope, they're all purring along (at least from what I can hear over the knocking noise coming from my motor...a story for another time).

Sniffed around the engine bay with starter fluid and with propane in an effort to chase vacuum leaks that didn't exist....after looking at the fuel trim data it points to a fuel delivery issue.

Basically it boils down to:

Long Term Fuel Trim hits the ceiling as soon as I snap the throttle open.

Getting into it on the highway with LTFT maxing at 25% and STFT also screaming for 15% on top of that (I'd imagine they're additive but I'm not sure).

I'm thoroughly stumped.

What do I check next?

Is there a possibility that a large exhaust would cause the o2 sensor to report a false lean?

I have a 2.5" side dump through an autozone rumble exhaust (thing was $30 don't look at me like that). It's all welded up except for the one clamp I used to stick the whole thing back on.

I can upload a datalog at a later time.

Thanks for reading

 

[cstarbard]

I am no expert but I have a few tips that I hope might help:

How I look for vacuum leaks is with a big cigar. I remove vacuum lines in different locations and breathe big puffs of smoke into the vacuum lines. Its kind of a redneck way of going about vacuum leaks but is actually pretty quick and effective, you see the smoke come right out of broken or cracked lines hoses etc. If you don't smoke, there are smoke machines that do this or maybe you have a friend with an affinity for cigars? Hell a vape might be even better haha

You can also get a cheap auto parts store vacuum gauge and test that way, also usually works pretty well

Also, a great way to look for intake leaks is to use brakekleen and an OBD2 scanner with a helper. While the truck is running, shoot brakekleen near intake gaskets, slowly and methodically. One person should be inside truck watching fuel trims on scanner, other spraying the brakekleen. If helper sees fuel trims spike when you spray a spot, take note of that- you likely just found an intake leak. On my brother's 3.0 we found a number of intake leaks this way that we otherwise would not have found. Good thing to test for; in my mind if fuel delivery is fine, and you have a lean code, it would make me wonder if you have an intake leak

I believe there are positive and negative fuel trims, positive meaning ECU is trying to add fuel, negative meaning ECU is trying to pull away, the former indicating lean condition and the latter indicating rich condition

 

[icetherice]

Ack I might try that to look for more leaks but the trim indicates that the ECU is trying to ADD fuel as the throttle opens. This is the opposite of the condition that would be observed if there was an intake leak because vacuum leaks are more significant at idle. This would be indicated by the fuel trims decreasing as MAF rate increased. I will not rule out a vacuum leak, however, because the idle still hangs around 1500 sometimes when the motor is still in open loop.

This is why I'm stumped, the engine screams for fuel as soon as the throttle opens but fuel delivery, and the other sensors, seem fine...I mean...I really don't want to start throwing parts at it.

 

[RonD]

Welcome to the Posting part of TRS

Fuel trims are the differences in Open time for fuel injectors, between what computer calculated and what the O2 sensor tells it about exhaust oxygen levels

0 fuel trim is the computers, on the fly, calculation of the open time for fuel injectors
This is based on air:fuel tables in computer software, then modified by MAF sensor, air temp sensor and throttle position sensor.

Computer then gets O2 sensor feedback and adjusts the STFT accordingly
+2% means injectors are being opened 2% longer than calculated to get O2 sensor in correct range
-2% means they are closing 2% earlier than calculated to get O2 sensor in correct range
And that's Short term fuel trim(STFT)

Long term fuel trim(LTFT) takes awhile to settle in if computer has been cleared and not used for awhile.
It purpose is to help computer run the engine when its cold, no O2 sensor feedback, or at other times when sensors are not working as they should.
LTFT will bias the air:fuel tables for current condition of the vehicle, so it can run, with smaller vacuum leaks or lower fuel pressure than it should have, which happens as any vehicle gets older.


I assume you have a 2000 Ranger with 2.5l Lima engine?

1998 and up rangers ran a returnless fuel system, computer expect 55-60psi fuel pressure at each injectors
If its lower then not as much fuel flows out when an injector is open, so computer must open injector longer, so +10% and up STFT would be seen

Yes, if ALL THE AIR going into the engine is not going thru the MAF sensor then computers calculations will be off, they will be low, so an air leak, or vacuum leak, will cause high STFT.

After engine is warmed up and idling, unplug the IAC Valve
Idle should drop to 500rpms or engine may even stall, either is GOOD, no vacuum leaks
If idle stays high then there is a leak

If you are using stock exhaust manifold, and upstream O2 placement is within a few inches of where it was before then I don't see a problem there.

Downstream O2 sensor is important as well for LTFT(not STFT), so it needs to be in place after a Cat, and should show stable voltage at about .7

Wandering idle is normal for the first few drive cycles, if engine was worked on
IAC Valve is a "learned" control, as is Throttle sensor and LTFT

When you 'step on the gas' STFT should go up above +10%, that is normal, but it should come down and run between -5 and +5 when cruising
Think accelerator pump on a carb, computer always opens injectors longer than 0 STFT, to get instant acceleration

idle will also run between +5 and +9 or so, computer runs engine Rich at idle so it won't overheat

 

[cstarbard]

OP: I think we are saying the same thing and that I phrased it badly; shouldn't positive fuel trims as throttle opens indicate a lean condition, meaning computer is trying to add fuel, which your code is for? In which case intake leak is possible cause?

http://www.easterncatalytic.com/education/tech-tips/fuel-trim-can-be-a-valuable-diagnostic-tool/

Also I don't think your exhaust has any effect on this issue, when I got my 96 2.3 the exhaust had fallen off from the cat backwards and was zip tied up by previous owner, connected to nothing... truck had no check lights driving this way lol

 

[icetherice]

STFT LTFT RPM MAF lb/min O2 Voltage
5.5 5.5 847 0.4 0.856
4.8 5.5 845 0.4 0.879
3.9 5.5 838 0.4 0.878
2.3 5.8 835 0.4 0.869
2.4 6.2 819 0.7 0.88
3.9 9 1336 1 0.919
3.9 13.3 3354 0.8 0.902
5.5 12.7 3159 0.5 0.81
6 11.7 2069 0.4 0.619
9.4 8.8 1884 0.4 0.135
9.2 4.7 989 0.4 0.29
6.2 4.7 970 0.4 0.705
6 4.7 871 0.4 0.77
4.7 5.1 855 0.4 0.885
4.2 5.5 827 0.4 0.885
3.1 5.5 832 0.4 0.885
2.6 5.5 839 0.4 0.864
1.6 5.5 834 0.4 0.863
0.5 5.2 864 0.5 0.844
-0.8 4.7 1235 0.8 0.694
-1.6 9.4 1386 1.2 0.095
-1.1 16.4 2007 1.9 0.079
2.3 21.4 1881 2.5 0.045
2.3 25 1574 2.6 0.072
2.3 25 1838 2.9 0.098
2.9 24.7 2173 3.7 0.065
3.9 23.4 2644 4 0.065
6.4 22.8 3269 5.1 0.06
10.9 18 3549 4.2 0.13
8.6 17.5 3685 1.4 0.879
5.5 16.4 2810 1.6 0.847
6.7 18.6 2812 2 0.46
8.6 25 2588 2.1 0.481
5.1 25 2367 2.6 0.819
0 25 2548 3.2 0.75
3.5 24.2 2565 4.3 0.065
8.6 21.9 2962 4.7 0.065
11.6 21.1 2997 5.4 0.075
15 19.5 3391 5.5 0.213
16.4 20.2 3449 5.8 0.74
15.9 21.1 3714 1.2 0.787
9.4 18.5 3583 1.2 0.91
8.8 15.6 3088 1.1 0.894
3.9 18.5 2948 1.2 0.865
4.5 21.4 2688 2.4 0.599
6.2 24.2 2736 2.5 0.368
3.2 24.4 2796 2.7 0.774
-1.6 25 2863 2.8 0.764
-1.6 25 2930 2.9 0.68
-1.5 25 3019 3 0.572
0 24.2 3033 3.1 0.2
0 22.6 3108 3.1 0.185
3.5 22.1 3117 3.1 0.1
6.2 21.1 3180 3.2 0.088
6.2 20.6 3203 3.2 0.065
6.7 20.1 3243 3.3 0.188
7.8 18.7 3270 3.2 0.334
8.2 18.5 3299 3.1 0.745
8.7 18 3326 3.1 0.755
9.4 17.6 3338 3.2 0.78
9.8 17.1 3367 3.2 0.589
11.7 15.6 3380 3.2 0.205
11.8 15.6 3409 3.2 0.19
12.5 15.6 3423 3.2 0.155
12.7 15.6 3454 3.2 0.261
13.3 14.8 3466 3.5 0.43
14.7 15.3 3488 4.7 0.252
17.2 17.2 3631 5.1 0.084
17.2 16.6 3642 6 0.714
17.2 14.8 3786 6 0.71
17.9 14.4 3800 6 0.675
19.3 13.3 3944 6.4 0.565
30.5 11.5 3970 6.8 0.13
30.8 9.4 4075 7 0.128
32 10.1 4143 7.1 0.125 THIRTY TWO PLUS TEN PERCENT ???
30.2 10.2 4260 7.3 0.414
25.8 10.1 4316 7.3 0.795
25.1 10.5 4430 7.5 0.795
22.6 14.1 4419 6.9 0.795
22.1 14.1 4394 1.2 0.828
20.3 14.8 3902 1.5 0.875
18.3 15.4 2943 3.3 0.834
11.7 25 2963 3.4 0.775
11.2 24.6 3002 4.9 0.715
9.4 21.1 3030 5 0.638
9.6 20.5 3063 5.4 0.3
10.2 18 3124 5.4 0.3
10.7 17.8 3126 5.4 0.308
11.7 17.2 3158 5.5 0.351
14.3 17.4 3190 5.7 0.75
17.2 18 3238 5.6 0.731
18.7 17.6 3251 5.6 0.66
19 17.1 3285 5.8 0.477
19.5 16.4 3306 5.8 0.238
19.5 16.6 3333 5.8 0.15
19.4 17.2 3376 5.8 0.215
15.6 16.9 3386 5.8 0.475
15.5 16.4 3427 4.1 0.576
13.3 16.1 3358 2.2 0.9
12.7 15.6 3129 1.4 0.881
9.3 16.3 2969 1 0.853
4.7 15.4 2764 0.9 0.845
4.1 14.1 2460 0.8 0.84
0.8 12.6 2337 0.8 0.83
-0.4 11.2 2085 0.7 0.825
-3.1 9.4 1880 0.7 0.819
-3.1 9.2 1666 0.6 0.804
-3.1 8.6 1284 0.6 0.807
-2 7.4 1244 0.5 0.82
-0.8 5.5 909 0.5 0.826
-0.8 5.8 886 0.4 0.85
-1.1 6.2 801 0.4 0.85
-3.1 5.9 810 0.4 0.85
-3.4 5.5 837 0.4 0.841
-4.7 5.9 828 0.4 0.825
-5.4 6.2 813 0.5 0.819
-6.4 6.2 817 0.4 0.808
-7.8 6.2 809 0.4 0.785
-8 6.2 783 0.5 0.773
-9.4 5.5 778 0.5 0.745
-9.2 4.6 764 0.5 0.698
-8.6 3.1 755 0.5 0.607
-7.8 3.7 742 0.5 0.075
-6.2 6.2 776 0.5 0.075
-7.3 6.2 817 0.5 0.382

This is the data from the third gear pull I made while testing the fuel pressure. Data is taken in .5 sec increments by the Lemur BlueDriver OBD2 scan tool.

 

[RonD]

Looks like LTFT started to average out toward the end


And O2 dropped to Lean
19.3 13.3 3944 6.4 0.565
30.5 11.5 3970 6.8 0.13 <<<<HERE
30.8 9.4 4075 7 0.128
32 10.1 4143 7.1 0.125 THIRTY TWO PLUS TEN PERCENT ???
30.2 10.2 4260 7.3 0.414 <<<<recovered here

Then went Rich again
25.8 10.1 4316 7.3 0.795
25.1 10.5 4430 7.5 0.795
22.6 14.1 4419 6.9 0.795
22.1 14.1 4394 1.2 0.828
20.3 14.8 3902 1.5 0.875
18.3 15.4 2943 3.3 0.834
11.7 25 2963 3.4 0.775
11.2 24.6 3002 4.9 0.715
9.4 21.1 3030 5 0.638<<<recovered here
9.6 20.5 3063 5.4 0.3
10.2 18 3124 5.4 0.3
10.7 17.8 3126 5.4 0.308
11.7 17.2 3158 5.5 0.351

LTFT needs to be learned over a long period, weeks

Check for vacuum leak
And test fuel pressure at idle and at 2,500rpm steady for 30 seconds

It reads like computer is struggling against a variable it can't control

 

[tomw]

Something funny in that data. follow the rpms ... for one thing. They do NOT climb over time without fallback. If there is acceleration, it is sometimes NEGATIVE acceleration. IOW, that must have been one weird pull. IMO. I'll shut up now and watch the experts...
tom

 

[icetherice]

Tom, good point. I probably had to back off during the merge for that one, I just went out now that it's late and there's less traffic, so I had plenty of room.

I attempted to test the fuel pressure again but for some reason I have problems with the autozone tester..I've only gotten it to read fuel a few times. When I hooked it up tonight I just kept getting 0psi even with the engine running.

LTFT is basically maxed for all of 4th gear.

STFT LTFT RPM Throttle ABS o2 Voltage
0.5 15.2 1752 21.6 0.244 << Third Gear
-0.8 16.4 1761 21.6 0.8
0 16.4 1797 21.6 0.786
-0.1 16.4 1809 21.6 0.465
-3.1 16.7 1857 21.6 0.449
-2.7 17.2 1879 21.8 0.39
0.8 17.2 1922 22 0.501
0.6 17.2 1950 22.3 0.825
0 17.6 1991 22.6 0.751
-0.9 18.2 2038 23.5 0.6
-3.1 21.1 2094 23.9 0.403
-1.3 21.5 2155 25.1 0.156
1.5 22.7 2226 25.8 0.81
-3.1 22.7 2321 27.5 0.61
-0.9 21.4 2405 41.5 0.08 << Ramp straightens out
3.2 10.9 2509 43.5 0.064 << LTFT is halved while the o2 sensor is reporting lean...?
8.6 9.8 2665 48.2 0.05 << STFT is doing about half the work
8.8 7.8 2734 49 0.051
14.1 8.4 2893 49.8 0.056
15.1 9.4 2980 49.8 0.08
20.3 9.4 3128 49.8 0.255
20.1 9.5 3208 49.4 0.765
19.5 10.2 3311 49.3 0.776
17.2 10.3 3450 49 0.773
15.6 10.9 3494 49 0.235
21.1 10.2 3590 49 0.353
21.3 9.3 3663 49 0.67
21.9 8.6 3745 48.9 0.713
22.2 8.5 3869 48.6 0.77
22.7 7.8 3880 48.5 0.754
22.7 7.8 3989 48.2 0.708
22 7.8 4032 48.2 0.495
17.2 7.8 4109 48.2 0.381
17.4 7.9 4172 48.2 0.16
18 8.6 4235 48.1 0.211
18.3 9.3 4328 47.8 0.298
18.6 10.9 4185 35 0.875
13.3 12.5 3549 17.6 0.871 << Clutch In
13 14.8 3317 18.9 0.85
9.4 16 2780 20.5 0.849
8.3 17.7 2774 25.9 0.845
4.7 22.6 2765 26.7 0.84
3.3 22.8 2764 29.4 0.83
0 23.4 2763 29.6 0.795
-1.6 23.4 2759 30.2 0.75
-3.9 23.4 2762 30.5 0.592 << Fourth Gear
-1.9 23.4 2765 31 0.433
-0.3 23.4 2770 31.7 0.335
-3.1 23.4 2778 32.6 0.298
-3 23.4 2788 34.1 0.15
-2.3 23.4 2802 34.1 0.133 << Fuel trims stable..LTFT near max under slow acceleration.
-2.1 23.4 2809 34.1 0.09
-1.6 23.4 2818 34.3 0.088
-1.6 23.4 2849 36.8 0.085
-1.6 23.4 2852 36.8 0.168
-1.6 23.4 2856 36.8 0.32
-1.2 23.2 2876 36.9 0.34
-0.4 22.7 2881 36.9 0.44
3.1 23 2891 36.9 0.526
3.1 23.4 2900 36.8 0.755
3.1 23.4 2910 36.9 0.751
2.8 23.3 2919 36.9 0.745
2.3 22.6 2928 36.9 0.716
0.4 22.9 2928 36.9 0.635
-1.4 23.4 2933 36.9 0.345
0 23.4 2940 36.8 0.369
0.7 23.4 2946 36.5 0.44
3.1 23.4 2953 36.5 0.563
2.8 23.4 2964 36.5 0.755
2.3 23.4 2966 36.5 0.758
0.2 23.4 2963 36.5 0.724
-1.4 23.4 2970 36.3 0.325
0 23.4 2983 36 0.413
1 23.4 2988 35.7 0.63
3.1 23.4 2994 35.7 0.695
2.2 23.4 3001 35.7 0.734
0.9 23.4 3004 35.7 0.64
-1.6 23.4 3006 35.6 0.532
-1.8 23.4 3010 35.3 0.31
-2.3 23.4 3014 35.2 0.282
-1.6 23.4 3027 34.9 0.287
-0.6 23.4 3031 34.9 0.54
2.3 23.4 3036 34.9 0.606
2.3 23.4 3043 34.9 0.755
2.3 23.4 3051 34.8 0.755
1.6 23.4 3067 34.5 0.751
0.6 23.4 3071 34.5 0.48
-2.3 23.1 3075 34.5 0.44
-2.2 22.7 3084 34.5 0.25
-1.6 22.7 3104 34.5 0.258
-1.6 22.7 3110 34.5 0.28
-1.6 22.7 3121 34.5 0.291
-1.6 22.7 3129 34.5 0.33
-1.6 22.7 3141 34.5 0.333
0 22.7 3153 34.1 0.34
3.1 22.6 3167 34.1 0.431
3.1 22.7 3183 34.1 0.535
3.1 22.7 3191 34.1 0.745
3.1 22.7 3204 34.1 0.736
3 22.7 3211 34.1 0.705
2.3 22.7 3220 34.1 0.685
1.1 22.7 3228 34.1 0.65
-0.8 22.6 3238 34.1 0.453
-0.3 22.7 3256 34.1 0.257
0.4 22.7 3257 34.1 0.405

 

[icetherice]

I put a vacuum gauge on my truck today. Held 20"Hg at idle and responded properly to a throttle snap. I sniffed around the engine bay with propane but did not identify any leaks.

 

[RonD]

The computer is also tasked with keeping the CAT converter(s) at a high temp so they can work, which means sending them more unburned fuel.
So STFT will be seen to go Rich and back to do this.

What does O2 Bank 1, Sensor 2 show as voltage, thats the after Cat O2, should stay steady around .7-.8 volts

 

[icetherice]

o2-2 spends a lot of time at .1v or less. There were seemingly random spikes I observed during the drive home. This was driving to the highway, then getting on the highway..not a true 'pull'. I'm not sure what response you should see from the post-cat o2 sensor during hard acceleration..if any? I hope posting the data like this isn't annoying.

Would this indicate a failure of the o2-2 sensor? What about an exhaust leak?

STFT LTFT MAF o2-1 o2-2
1 4.6 0.4 0.565 0.075
-0.8 3.9 0.4 0.532 0.075
0.2 4.1 0.4 0.44 0.075
1.6 4.7 0.4 0.362 0.075
2.3 4.7 0.4 0.24 0.075
2.6 4.7 0.4 0.16 0.073
3.9 4.7 0.4 0.201 0.07
2.5 5.7 0.4 0.755 0.07
0 12.5 0.9 0.551 0.07
2.2 12.1 1.3 0.085 0.07
4.6 10.9 1.4 0.419 0.071
3.1 10.9 1.5 0.847 0.075
4.2 11.4 1.6 0.101 0.073
6.2 14.1 1.9 0.344 0.071
3.2 14.3 2.1 0.835 0.075
1.4 14.8 2.6 0.522 0.075
4.7 16.3 2.7 0.262 0.075
4.3 18 3 0.755 0.077
3.1 19.5 3.1 0.765 0.08
2 19.4 3.3 0.82 0.08
-1.6 13.3 2.3 0.622 0.093
0.8 12.8 1 0.075 0.469
3.9 10.9 0.8 0.365 0.449
4.7 11.6 1.1 0.773 0.37
4.5 12.6 1.6 0.86 0.434
3.9 14.1 1.8 0.853 0.514
2 14.1 2.1 0.835 0.49
0.1 14.1 2.1 0.828 0.546
0.8 14.7 2.2 0.817 0.694
0.9 15.6 2.5 0.735 0.67
1.6 16.6 2.6 0.729 0.615
1.6 18 2.9 0.6 0.588
1.6 18.3 2.9 0.601 0.535
1.3 18.7 3.1 0.705 0.51
0 18.8 3.1 0.699 0.465
-1.1 18.9 3.1 0.45 0.394
-3.1 19.5 3.1 0.55 0.316
TL;DR

 

[icetherice]

I tested the fuel pressure again. Rock solid at 63psi even holding 2500rpm for 60 sec. I think it's either the MAF or the o2 sensors.

 

[icetherice]

This is a 3rd geat pull at basically WOT, after patching some exhaust leaks today and looking for vacuum leaks again, and ensuring the fuel pressure is not the problem...

STFT LTFT RPM o2-1 o2-2
2.9 14.1 2334 0.062 0.065
7 14.4 2337 0.094 0.065
6.6 14.8 2340 0.598 0.063
4.7 14.8 2348 0.588 0.06
5.3 14.8 2364 0.478 0.062
7.8 18 2394 0.508 0.065
5.4 18.2 2449 0.823 0.068
0 20.3 2495 0.628 0.071
2.6 20.9 2551 0.145 0.075
5.5 22.7 2636 0.435 0.076 << long term is happy here, crack the
6.2 19 2731 0.707 0.08 throttle, ltft and stft switch places
7.6 14.8 2873 0.05 0.066
13.2 11.7 2939 0.052 0.045
14.5 11.7 3112 0.065 0.043
20.3 10.5 3179 0.092 0.04
20.3 9.1 3309 0.24 0.045
20.3 7.8 3422 0.209 0.05
24.7 7 3538 0.14 0.055
28.4 5.5 3685 0.467 0.063
29.6 5 3760 0.729 0.075
30 4.3 3873 0.789 0.081
30.5 2.4 3983 0.718 0.085
28.2 2.7 4090 0.605 0.085
28.2 3.1 4217 0.255 0.085
35.9 3.9 4290 0.345 0.085
35 4.4 4392 0.66 0.201
33.1 6.3 4341 0.735 0.417
25.7 8.3 4188 0.818 0.834
24.5 11.2 3584 0.878 0.863
21.1 14.1 3366 0.877 0.895
18.4 14.1 3083 0.864 0.898
15.2 14.1 2750 0.861 0.901
10.9 13.7 2694 0.855 0.904
9.9 13.2 2452 0.852 0.905
7 11.7 2309 0.839 0.905 << up and downstream pegged rich after
1.2 11.1 2118 0.81 0.904 throttle closes for multiple seconds
-3.3 10.2 1791 0.721 0.898
-3.9 10.2 1611 0.703 0.888
-3.9 10.5 1430 0.74 0.874
-3.7 10.9 1289 0.744 0.875
-3.1 10.9 1269 0.77 0.875
-4.3 10.1 1215 0.813 0.875
-5.5 7.9 1116 0.79 0.879
-6.6 4.7 949 0.764 0.88 << stft responding to 'learned' higher rpm
rich state?

 

[tomw]

Have you checked the TPS sweep for dropout and glitches? Have you looked at the MAF for contamination on the wires? I am too lazy to go back and re-read the other 13 posts, so there's no spider nest in t he MAF like I just saw in a recent post somewhere.
Looking at the O2-2 numbers... it seems that it starts low, gets some upper numbers in the first 1/4(ballpark) of the listing, then falls back into low numbers. Low numbers indicate a 'lean' condition, IN THAT THERE ARE O2 molecules floating past the sensor. If you have a leaky exhaust system, you may just ignore the O2-2 numbers as they would seem to be invalid. Opinion only...
(Wish the numbers could be aligned under the column headings rather than being so wavery- much easier to read & digest)
tom