Code P0171, High fuel trims across all engine speeds, poor acceleration?

Additionally, since the engine will not take throttle without increased fuel, I do not believe it is an air leak in the exhaust near the O2 sensor.

Hello, a couple things come to mind, with the very high mileage I would do a fuel injector balance test and see if they are all flowing the same. But I suspect a cat issue more than an injector issue. Although I would test for both, doing a back pressure test a the from A/F sensor location would tell you if there's a restricted exhaust. If the back pressure is over 2psi, which if that's the issue in this case it will be much higher. With such a small engine, the cat doesn't need to completely melted down to cause issues. Since you have already pretty much checked everything except the injector flow and the cat. Being that I believe the cat is part of the exhaust manifold on these, testing back pressure at the front A/F (02) sensor is the only real way to verify a restricted exhaust, I believe there is a 2nd cat half way down the exhaust as well that does not have an 02 behind it if I remember correctly, I'll check that in service info for you.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Okay, it looks like this isn't the model with the cat being part of the exhaust manifold, which must be a different year I was thinking of.

Interestingly though, there is a valve adjustment for this engine, it's the more difficult method of measuring and adding different size shims. But you could take the valve cover off and look for any worn cam lobes, after checking the back pressure and injectors. You might just be dealing with clogged injectors or a bad tank of gas, with everything you have already done, you're only left with a couple possibilities now. Harbor Freight sells a vacuum gauge that also measures positive pressure up to 10psi, that's what I use with an old 02 sensor bored out as an adapter to measure back pressure at the front 02 location. Just don't leave the gauge on there more than a few seconds to measure back pressure or it will melt the gauge. Hook it up, have someone else start the engine, check it at idle, and then have them try to rev it a couple of times while you monitor the gauge. then shut the engine off. You'll know right away if there is excessive back pressure.

Okay,, more background. I recently (within last 10k miles) replaced the catalytic converter. It is located inline directly downstream of the exhaust manifold. The car ran fine afterwards. I will check the exhaust back pressure regardless. For my own knowledge, I have read that exhaust back pressure does not affect fuel trims so does this fit with the symptoms?

For my knowledge can you explain how worn cam lobes would result in the symptoms I am seeing?

I wasn't saying what you're experiencing is a result of worn cam lobes, which was just because of the very high mileage it has. The symptoms do fit a restricted exhaust, but if this issue has been on going since the cat was replaced, then that's not going to be the problem, I do wonder though what the condition of the previous cat was like. Did it come out in pieces, such as happens when one melts down and breaks apart? I have seen a broken cat come out but chunks of it get stuck in the rest of the exhaust, and if not checked would still be a restricted exhaust even with a new cat on there.

Just looking back over your list of repairs so far, you had listed the AF sensor as reading 1.23, is that milliamps?
And what is the reading of the rear 02 sensor at idle, and at 2000rpm if you can get it to go that high?
Since you have good scan data, some other things to check would the MAF reading at idle, on a small engine like this, it should be roughly around 1.3-2.3 grams per second or so (that is right from service info), (2.3g/s) at idle and 5.4-7.9 @ 2500rpm, on larger engines as a rule of thumb it will be about the same as the liters of the engine, so on a 5.0Liter it should be about 5g/s at idle.
And another test to run is a VE Test, here is a link to a good VE calculator.

https://atgtraining.com/atg-volumetric-efficiency-calculator/

This is a screenshot of the page, when you input your live data PIDs, it will calculate the EST_VE which is the Volumetric Efficiency of the engine, basically how well the engine is breathing, taking in air and allowing exhaust out. If you have a bad cat, or a MAF that is misreporting air flow the VE percentage will be low. You want the number to be as close to 100% as possible, it won't be, but for example the 94% is really good. The Instructions go through a bit more about the test. It's a helpful test to have in general,

But I agree with your diagnosis and thought process so far, the only thing that looks out of place is your AF sensor reading, on a Toyota it should be reading about 3.0 volts on an engine that's running at the correct air/fuel ratio, so that's why I asked about your reading there. If it's in milliamps or if that's the sensors voltage reading.
If it is reading 1.23volts at idle, that's way out of spec. I'm going to post the flow chart for you of the AF sensor's service info., I'm wondering if the parts store gave you either the incorrect part number or possibly a regular narrow band 02 sensor. Service info here is stating that anything under 3.0volts will cause high injection volumes (ill post all this for you). 25%+ which is what you are seeing.
And I know that Toyota's a really good at detecting oxygen sensor heater circuit issues, I've been down that road before. And you're not getting any heater circuit codes. So let me get this flow chart together for you, and you can go through it page by page and check your scan tool data.

Okay, so some of these scan tool data PIDs will depend on if you are using a Generic basic OBD2 scan tool in which the AF sensor voltage will be converted into a lower reading such as 0.62volts to 0.7volts. If you are using a scan tool and are on the Toyota manufacturers side reading live engine data you should see about 3.0volts on the B1S1 A/F sensor, so either way, something does not look right if that reading is in voltage.
I'm not going to post all of this since you have already checked a lot of it, but these first diagrams are for checking the manufacturers side of the scan tool, so selecting 2007 Toyota Corolla 1.8l etc. It gives a voltage reading of 3.0volts as being 14.7/1 ratio (normal). Page 4 shows that service info. I'll post the basic OBD2 data next.

This is the generic OBD2 scan tool flow chart for P0171, and it pretty much ends in "Replace the A/F sensor", and then "Replace the ECM". So, the only differences are the Output voltage readings. But this gives the same MAF readings. I haven't seen a Toyota AF sensor voltage drop that low on the manufacturers side of a scan tool, such as on an Autel or Topdon. Service info states the ECM converts the current flow into a voltage reading for live data, but I suppose that could vary depending on scan tools as well.

Okay, for CAT questions the old cat was nearly 100% plugged off but not broken. I spent some time looking at the service manual and it is terrible for giving details on specifically what each part is in the exhaust. There are three "wide spots" in the exhaust system before the muffler. The first one is the CAT. It has the secondary O2 sensor behind it. According to online searches the last wide spot is a resonator. I can find no information on the middle wide spot. I see it appears on aftermarket CAT pipes but I am not sure of its purpose. My new CAT pipe has the second wide spot on it so if anything broke off its in the resonator or muffler. I will tap on them to see if I hear anything moving in addition to the back pressure test.

I have a Autel MaxiSys 909 scanner. It reports voltage and a ratio for the AFR sensor. The value I reported is the ratio. As I understand it higher ratios (above 1.0) are lean, and lower ratios are rich. A ratio of 1.23 corresponds to 4.99V as I watch it on the scanner.

MAF readings:
740 RPM = 2.35 gm/s
2536 RPM = 10.62 gm/s

I will run the back pressure test, and retest the fuel pressure on Friday. Additionally, I will review this correpondence to see if there are other tests I need to run. My issue is if the ECM has not relearned the particular area of the fuel map to the ~150% fuel increase then the engine falls flat when I hit that area. If I full throttle the engine (open loop) the engine barely runs. This implies to me it is real (meaning not a sensor lying about the engine being lean when it isn't). If it was a lying sensor (say AFR) then the engine should run fine in these unlearned areas despite the sensor reading.
Lets say it was an air leak. It would seem to me that in order to have full fuel trim values (~150%) across all engine speeds the car would either idle extremely high or not run at all without holding the throttle down. This seems unlikely.
So I ask myself what causes high fuel trims across all engine speeds? If you think of anything else let me know.

Note: the 2500 RPM MAF value above was with AC on. I re-ran the test -
MAF readings:
737 RPM = 2.14 gm/s
2506 RPM = 7.73 gm/s

Yes,you're correct, if it was an air leak (vacuum leak) it would cause the fuel trims to come down towards zero at WOT, along with being in open loop, manifold vacuum would be closer to atmospheric pressure and the leak wouldn't effect fuel trims like they are, so yes it appears to be an actual lean condition. Your MAF readings suggest it's okay. They were a little better on the first pull, but still within spec. The AF ratio of 1.0 is stoichiometric (14.7/1) so 1.23 is an actual lean condition reading as well, you might be looking at clogged up, restricted injectors here.

You've really gone through almost everything, if an injector balance test shows different flow rates between the 4 of them, then you'll know there's at least an issue there. Really they should all flow exactly the same, have you done an injector balance test with a fuel gauge on the rail before? Where you get fuel pressure up to its max, then pulse each injector one at a time and watch for how much the fuel pressure drops on each injector. It requires an injector pulse tool or your Autel might be able to do it under special functions. You just need to re-prime the fuel pump each time, and once you run through all 4 injectors start the car to get the fuel out of all the cylinders, then you can re-run it again if needed. But if you find the fuel pressure drop is even a few psi off from other injectors, you know there's an issue there as well.

I think the ECM is at its complete limit for compensation, it just can't go any more than that percentage, it's a substituted value but extremely high, I think service info stated a 35% (or +25%) was the limit on positive fuel trims.

You could also graph the rear oxygen sensor voltage, and it should go full rich (high voltage) at a WOT run, and then it should have an injector cutoff when decel, my guess is you are going to see the rear 02 go lean instead. The MAF readings should be lower if this was a restricted exhaust, because the engine would not be able to take in more air if it can't let exhaust out.
As for the ECM being the problem, I would definitely rule out the injectors and back pressure first, making a call on an module is always a last resort and a difficult call as well. Because if a new ECM makes no difference you're back to square one. I'm surprised it's not setting other codes.

Whats your injector on time (pulse width) at idle? I'd think 2.5ms to 4ms for an injector pulse at idle should be about right and WOT I would guess 15ms +. Thats another way you could see if the ECM is really compensating for this condition. Honestly it's nice to be able to have someone who understands these terms, having to explain all this can take weeks sometimes.

One last thing I've been doing in past few years is going through the Mode 6 data. If there's something that is close to setting a code but not there yet, it will show in the mode 6 data list, Autel shows a good list of it all. Just look for "OK" or "Failed" in the test results. And even the number is gives for the test result can give you a clue as to what monitor is close to failing its self-tests, it will give a min, or max, and the test result number.

This is an example of the injector pulse tool, this is a cheap one, but they work pretty good, as long as the pulses are even. Here's a video on running the test, if you're unfamiliar with it.
Let us know what you find next. Sorry for the long post.

https://www.youtube.com/watch?v=K7STocr9FBI

Fuel pressure test results -
Engine off: 48 psig
Park, Idle cold: 48.5 psig
Park, Idle hot: 48.5 psig
Park, 2500 RPM: 48.5 psig
Park, full throttle: 48.5 psig

Exhaust back pressure test -
Needle bounces around zero at idle and at 3000 RPM. Pressure easily below 1 ¼ psig.

Downstream O2 test -
Park, idle: 0.075 V
Park, 2500 RPM: 0.055V

I have posted my injector test results in here twice and they keep disappearing?

Injector test results -
NOTE: fuel pressure drops continuously (slowly) when I turn the pump off. I have previously tested this and I have a leaking check valve.
Inj #1: 40 to 37 psig
Inj #2: 40 to 37.5 psig
Inj #3: 40 to 36.5 psig
Inj #4: 40 to 37 psig

I now have an additional engine code P0302 for cylinder #2 misfire. It does not move with a coil position change nor with a new spark plug. I may have run this thing lean too long.

Injector pulse width test -
Park, idle, hot: 3.7 ms

Injector tests above run on mode 2 on injector tester:
50 pulses at 7 ms pulse width

Photos

Okay, just taking a look at all your postings here, looks like the back pressure is not an issue, that seemed to be the case with the live data from the MAF.

So when was this 3rd set of data PIDs done? This is the strange(r) one of the bunch, its looks like at idle, and 186.8f on the ECT. But Throttle Position is at 80%? and injector on time 10.4ms? And this was taken in Open Loop. Something just doesnt look right here. It looks like closed loop is when the super high fuel trims come in, can you grab data PIDs ECT, Fuel system status, STFT & LTFT, RPM, TPS, Injector ms, MAF, calculated load, B1S1 & B1S2, just those data PIDs, and any others you think will help. I think we need to see what the MAF is reporting during some of this, because how can you have 80%tps @ 650rpm? With the injectors being almost full on at that point, the only difference I see here is the Open/Closed Loop difference. Im going to see how this MAF reads, if its frequency or voltage reading, Interesting case study, Im going to go through the sensor operations some more. You may want to Graph the TPS and check for anything weird going on there too. I cant explain these specific readings at these certain engine temps. I would think at 186.8f it should be able to go into closed loop at that point.

I named the photos for the cases but apparently that does not show up. The specific case you are asking about is a full throttle case in park. Since the fuel map has not "learned" that position and I am in open loop the engine just bogs.

For the regular idle case you can see the fuel map has dramatically increased the fueling (~150%) and the injection time (ms) is higher than it should be. To me this agrees with the lean O2 readings I am receiving.
Any other ideas on what could cause this? I have not researched the effect of cam advance/retard on O2 readings. Lets suppose the timing chain has stretched or the hydraulic advance mechanism is leaking, would it have any effect on O2 readings?

Yeah, I can see the fuel compensation has maxed out in closed loop which is your 4th picture up top there. The rear 02s are only going to read oxygen or lack there of, not the amount of fuel.
But in the picture 3 you are going WOT to 80%, the ECM goes into open loop like it should, the pulse width goes high like it should, the AF sensor ratio of 1.23 though is indicating on the lean side. **But is the lack of RPM change the bog down you are referring to?
Just curious, where did the AF sensor that you swapped out come from? Because it's pegging out a 4.99volts there as well during that event. This data just looks so out of place here.

I mean a stretched timing chain is a possibility, Id think you would get some crank/cam correlation codes, along with some possible back firing into the intake, but that also depends on how stretched it is,

Do you have a 2 channel oscilloscope where you could grab the cam and crank signals, I can get you a known good cam/crank wave form for this vehicle no problem, and we could compare the two, I would need your waveform first, Ill give that to someone I know and he will give the same waveform back at the same time base and such. We're only dealing with one cam sensor, if you can get a waveform which shows 360degrees of crank rotation, so you'll have 2 crank TDC signals, one at the beginning of the waveform and one at the end, with the cam signals below it, and zoomed in enough where we can measure the actual degrees between either the rising edge or falling edge of the 2 sensors, that would tell us exactly how stretched the chain is.

If you have an in-cylinder pressure transducer, that can even tell you if your intake or exhaust valve opening is either retarded or advanced. I use a scope for almost everything these days.. I can post some examples if needed

So this is a cranking in cylinder waveform from a 2006 Honda CRV, which turned out to be a strange head gasket issue, but even though this is not a crank/cam waveform it shows how we could measure the degrees between the two signals my lining up the cursors and marks, the compare it with a known good, do the same and see if there is timing chain stretch or if the timing might have jumped a tooth, but in that case technically it should set a code, but sometimes the difference needs to be something like 5 or 6 degrees to actually set a code for timing, This is from a Pico scope setup. I just put this up as an example. I do have a vehicle here that I need to get the cam and crank signals from, which I'll try to do in the next day or so.

Did this car come to you like this? This isn't a personal vehicle, correct? If it's a customer vehicle I might question if they did any work previously, that rear 02 is staying full lean all the time, is that thing shorted to ground somewhere? Maybe melted a wire to the exhaust or something, in every set of data it's pretty much looks grounded. I've been so focused on this insanely high fuel trims, but going through each picture, it's stuck there. 0.055v all the time, this will be embarrassing if it's just a bad rear 02 or its wiring.

Unplug that rear 02 sensor and see if scan tool data goes to 0.450mv....Sorry I should have had you do this to begin with, I think I went down a rabbit hole on this one. I apologize for that.

To answer your first questions -
Yes, bog means the engine just sags with no power and often the RPM, drops.
The AFR sensor I bought new in Bosch. It gave basically the same readings as the original.

The car is mine - my daily driver. The rear O2 sensor moves when you rapdily decelerate the engine as you would expect.

I can theck the rear O2 reading unplugged but I have always read that the rear O2 is not used for fuel trim adjustments, just for CAT health.

So from your reply it is unlikely to be a timing or advance/retard issue as a code would be set. Any other ideas? I am out of things to check.

Yes, you're correct, the rear 02 is really only for Cat monitoring, but the way it's almost 0 volts all the time, it should be around a steady 600mv roughly, go rich a WOT and go lean on decel. And this brings us back to the fuel injectors, but one other thing to check first is to block off the Purge valve and make sure that the condition is still there with the Evap just deleted off for testing. If you block off the port on the intake for the purge hose, and you still have huge fuel trims, we are really left with injector flow. I was thinking about this car all night, you've got good fuel pressure, no sensors are coding, and Toyota is pretty good at setting codes. I know you did and injector balance test already, but we have gone through almost everything.

So, Id first check to make sure the injector power wire can carry current, the injectors and coils look to be powered directly through the ignition switch (I will verify this), but they are on a 15amp fuse, so that injector wire should be able to light a 4amp test lamp easily. I use a turn signal or headlamp bulb should work, I use a turn signal bulb, one filament is about 2-3amps for load testing wiring. If it can light the bulb with no problems for a few seconds, then at least the wiring should be okay. I don't even think a purge valve stuck open would cause the fuel trims you're seeing, they're just too high.

Plus, your sensor data points to an actual fuel issue, so the *injectors and *fuel rail, Or *bad gas is all that's left. Unless we missed something, I've been crossing off components listed under the p0171 code criteria, and we're at what you see below. You did smoke tests, I'm not sure how much pressure you put on the intake while smoking it, but a vacuum leak should go away at higher rpm and this issue isn't.
If your power feed load test is good, I guess pull the rail and you can even use the injector balance tool to see what they are flowing.

Something else I've seen which is common these days, is if the injectors have been replaced by someone in the past and they install the "great deal" injector set from amazon, or some other aftermarket source, and they are junk and just don't have the correct flow rate. Or if the incorrect injectors were installed at some point,
I mean between the 2 of us, this shouldn't be too difficult, it's just the amount of trim that's really crazy, You're correct the fuel mapping is maxed fully. This leaves the fuel rail, and I'm really looking forward to hearing the fix on this one. I have to go on a mobile call here shortly, but I will stop back and check your reply during the day.

Okay, I will have to wait for the weekend to perform the injector test. Another symptom I thought of is the car is easy to start when cold but very difficult to start once iit'shot.
I have already performed the purge hose test as well removing the hose to the brake booster and PCV - no change.

Ok, I think the cold start symptom has to do with it being in open loop at that point, because everything changes when it goes into closed loop. But in open loop your scan data showed the 10.4ms injector pulse and almost no fuel trims, but then into closed loop at 190f degrees and idle speeds the injector pulse is down to 3.7ms and fuel trims off the charts. Service info does have this Initialization procedure but its a road test relearn type of procedure. That total fuel trim is 64.4% positive, that's a crazy number.

This vehicle is definitely the difficult one of the month, that's for sure. I feel like we are missing something here though, just curious what's the max voltage the rear 02 goes to at any point? And you're 100% sure there are no exhaust leaks? a method I've seen a tech use once was to hook a shop vac to the end of the exhaust pipe and switch the hose around to the side of the vac that pushes air out, so it's really pressurizing the exhaust, then go around and spray the exhaust sections with soapy water to look for leaks that were hard to detect, because the smoke machine just wasn't enough pressure. This was a master tech as well doing this.

I have run into that as well, high fuel trims around +15% and I smoked the intake multiple times with no leaks, then I upped the pressure a bit more and finally started to see small puffs of smoke coming from many fuel injector seals. It wasn't a crazy amount of pressure, but more was needed to find those leaks. The only system that cant take over a couple psi pressure is the Evap system, but the only difference with my injector leak diag was that it was acting like a vacuum leak, fuel trims would come down at 2500rpm. And yours are not. I'm going to check with someone on this, he will probably know what's up right away.

Do you get the same readings if you switch your scan tool over to generic OBD2 data? Not the manufacturers side

I do not think its an exhaust leak as it goes into open loop at WOT and the engine just bogs. At WOT it should not be using AFR feedback.

I agree with your previous estimate that it is fuel related. I intend to pull the rail and look at the injector patterns. If they are not clogged, then I am out of ideas.

Yes we're on the same page. WOT should go full bore... I messaged a friend of mine whos a sales rep for PicoTech but he didnt get back to me yet, he might not have an answer since you have already gone through so much. I mean we are only left with injector flow or bad ECM I think. I kind of wish I was at this vehicle to see how its acting, pretty interesting case study if its all 4 injectors clogged up,. Did the car sit for awhile, or did these issues develop over time? Its amazing how high the mileage is,

You want to pump out a gallon or two out of the tank when you have the fuel lines apart and let that sit. If theres anything in it but gasoline it will separate into different levels in the bucket, just to see if there is possibly anything in the bottom of the tank. This will also show how much volume the pump can put out.
But also load test the injector power feeds with a good size light bulb to make sure they can carry good current. Pop out a turn signal bulb if needed, that should be 2-3 amps at least. Port fuel injectors only pull about 1 or so amps if they are the 12-14 ohm ones. So a turn signal bulb is plenty to see if that circuit can carry enough current. but only keep it lit for a few seconds. I cant wait to see this thing fixed man..
These are the injector power feeds, the Black/White wire also feeds the coils, its strange that it comes directly through the ignition switch and not from a relay, but diagrams 4 and 5 are the "oem" if theyre correct,