I would think the same - sticking EGR, lazy fuel injector, O2 (or AFR) sensor. Anything over 150k+ miles / 10 years on the sensor would be a consideration in suspecting it. Same w/ Ignition (tune-up) items: plugs, wires.

re: LTFT not changing: that could be a number of factors, including scan tool used, ECM buffering trim values, etc.

I would clear all codes and take it for a ride to further diagnose / and review the LTFT update interval.

Hope this helps.

 

LTFT takes several minutes to change. STFT has to stay positive for a while, then LTFT will start changing to bring STFT closer to 0.
Need more details. mileage? health of engine? age of o2 sensor? age of spark plugs?
There are ways to test O2 sensors, find some vids on YouTube. If in doubt and O2 is original, just replace.

 

Thanks for the quick reply!
I just rebuilt the engine 2001 5f-se 1000 miles ago.
The car only had 71,380 miles on it when I picked it up. My wife wanted this car for her work to save gas and it’s a automatic, she works for hospice and does a lot of driving.
It was supposedly a blown head gasket but it turned out It was a busted head because somebody put water in it and it froze. Long story short I’ve completely went through it with a fine tooth comb. I did have to deck the block it was .003 deep in the middle. I suspect it was overheated .004 got that out also magna flux the block to make sure there was no cracks.
I did re-use all the sensors and fuel injectors and the coils that came on it. All new wires and plugs I used the NGK double electrodes that Toyota said to use. New air and fuel filter I cleaned out all the EGR ports very little carbon,The EGR diaphragm seems to be working fine with a vacuum gage it holds vacuum The engine was very clean with hardly any wear, it was all within the middle of all the specs.
I basically got a used head and did a valve job and pressure tested and vacuum tested and made sure all the cams and lifters, guides was in spec and I’m happy with that. I re-ringed it basically and after I dumped the break in oil out 500miles later I did a compression test to see how the ring seated I got 193 across-the-board.

500 miles later I’m getting p0300 and the first thing I did was hook it up and I seen it’s not getting enough oxygen in the exhaust. I pull the brake booster line and it stays rich -17 on the LTFT
I cleared the codes yesterday and drove about 50 60 miles and it still -17 at idle. When driving isee it go to-10 under hard acceleration but mostly stay-17 no matter the rpm or load.
I’ll see if I can find all the specs for the different sensors and just go from there when she brings the car home. I thought maybe it was just a common 02 sensor failure thing for negative long term fuel trims and not really changing but STFT did change. I think this is a narrowband system?
I’ll tell her to drive something else tomorrow so I can figure out what’s going on if I can find the specs on the different sensors.
I only have engine spec data for it.
Don’t want to shoot a parts cannon at it and I’m still learning on diagnostic trouble shooting on sensors. Sorry for the long reply but that should answer most questions I hope. Thanks for the help!

 

If the O2 sensor was on the (original) engine, and given LTFT is not adjusting regularly on the scan tool - yeah, if it was here, I'd be replacing the O2 (or AFR, if a Cali. emissions vehicle) B1S1 sensor, first. ... After checking connector / wiring to ensure condition, etc. as a 'sanity check' / before purchasing replacement.

^ Going by your posts above, given that the motor is not experiencing high idle (indicating vacuum leak), or other drive-ability issues. You seem confident in the motor / your work, and the compression #'s confirm that. LTFT is directly derived from the O2 (or AFR) sensor via ECM, so yes - that's the sensor responsible. Hope this helps.

 

O2 sensors don't last forever. While 73k mi it should still be "fine", I'd just throw an O2 on it regardless - they are considered a consumable item on these engines and go do bad. While your concern is valid, I would not consider that a parts cannon shot.
Since you're getting P0300 rather than a specific cylinder, and RPM range does not affect LTFT, I would rule out a leaking injector. The only other thing would be ECU, but that is rare.
Also, check freeze frame data if you still have it, in case it's something stupid like a coolant sensor that's caput and forcing the ECU to work in cold engine fuel enrichment mode.

 

Thanks guys for all the help. I’ll definitely give everything a good look over tomorrow. She’s off tomorrow and I’m pretty much not busy tomorrow. She got home a few hours ago and said it came back on today p0300.
I did pull the freeze frame data and the ect was 205 degrees and STFT b1 was 2.3% and LTFT b1 was 17.2%
So I believe the ect sensor is correct. I did yesterday unplug the ect and it went to -40 instantly and throwed a light for it.
Again thanks everyone for the help.

 

You don't mention if you have the 4 cylinder or the V6 but your Camry's TCCS computer-controlled engine utilizes its MAF, MAP, IAT, ECT, O2, A/F, etc and other sensors to maintain a stoichiometric AIR-FUEL ration of 14.7:1, and will control the fuel injector pulse width to maintain this stoichiometry. But the (random) cylinder misfire code of P0300 is telling, and that your fault is not specific to just one cylinder, so you might be suffering from misfires in all cylinders. I would try running some FUEL INJECTOR CLEANER through your gas tank and see if you can clean gummed up injectors, especially if the car has sat for long periods of time without operation. Your injector(s) may be just gummed up with old fuel.

Fuel trim values in the negative on the long term fuel trim (LTFT) is a response to too much fuel being introduced (RICH condition), and if you are running at -17.2% it is very possible this is an accurate reading and is considered the "new learned value" (input/output to the ECM LTFT table) in order to compensate for too much fuel. Use the scan tool to monitor "live data" and watch for any trending data on either the STFT or LTFT values. Upstream O2 sensors will oscillate from 0.1 vdc to 0.9 vdc in a constant sinusoidal waveform. Downstream O2 sensors will maintain a much more steady DC voltage value and remain fairly constant in a properly operating engine.

It's likely the most obvious fault would be leaky fuel injector(s). I would not parts-cannon the O2 sensors as they sound like they are outputting accurate data to the ECM. Use your scan tool and look at the STFT and the LTFT live data in conjunction with each other on the bank you are concerned with (I assume you have the 4 cylinder engine). A MIL error code is not set until around 20% or more for FT's, so your check engine light may not yet be illuminated for this fault, but the P0300 is sensing that something is amiss with your engine.

FYI: Here is some general Fuel Trim information that applies to all computer controlled engines:
(If the vehicle runs out of fuel, the air−fuel ratio is LEAN and DTC P0170 is detected. The MIL then comes on. Fuel trim applies separately to bank 1 and bank 2, so the ECM lights up the MIL if a problem occurs with either bank.)

You can tell which bank is malfunctioning by looking at the short−term fuel trim and long−term fuel trim, thus allowing you to focus your inspection. If the total of the short−term fuel trim value and long−term fuel trim value for each bank is within 25%, the system is functioning normally.

”Fuel trim” refers to the feedback compensation value compared against the basic injection time. Fuel trim includes short−term fuel trim and long−term fuel trim.

Short−term fuel trim (STFT) is the short−term fuel compensation used to maintain the air−fuel ratio at its ideal stoichiometric value. The signal from the heated oxygen sensor indicates whether the air−fuel ratio is RICH or LEAN compared to the ideal stoichiometric value, triggening a reduction in fuel volume if the air−fuel ratio is rich, and an increase in fuel volume if it is lean.

Long−term fuel trim (LTFT) is overall fuel compensation carried out long−term to compensate for continual deviation of the short−term fuel trim from the central value due to indivual engine differences, wear over time and changes in the usage environment.

If both the short−term fuel trim and long−term fuel trim are LEAN or RICH beyond a certain value, it is detected as a malfunction and the MIL lights up.

 

How to check injector injection: Remove the delivery pipe and injectors from the bank that has the malfunction.
Check injection volume of injector:
1. Injection volume: 56 − 69 cm3/15 sec. (3.4 − 4.2 cu in.)
2. Difference between each injector: Less than 6 cm3 (0.4 cu in.)
3. Fuel drop (leakage): One drop or less per minute.

 

It is the 4 cylinder 5sfe
I did see on the scanner that the voltage for the 02s b1s1 is 3.255volts
02s b1s2 is .670volts
STFT b1s1 is 99.2%
Lambda b1s1 is 1.000
don’t know if that helps anything because I kind of understand what’s going on but not entirely.

I always thought 02 sensors just measured the oxygen in the system. Less air means rich and more air means lean.
I found a good bit of specs for sensors I’m going to check them out tomorrow. Thank you for the injector specs.
Car runs good so if I can figure it out,she will drive it tell it don’t go anymore. So far it’s getting 27mpg and if the light didn’t come on you would never know anything is wrong. Might have to invest is some good diagnostic tool for my self. It won’t help at work but it would around the house.
The only specs I have the engine. They don’t tell you anything else about them.

 

I did see on the scanner that the voltage for the 02s b1s1 is 3.255volts

That voltage on the scan tool would indicate the B1S1 sensor is -not- an O2 sensor, but an Air Fuel Ratio (AFR) sensor, aka: "wide-band" sensor.

That is what I would confirm first: does the vehicle have a B1S1 O2 sensor, or an AFR sensor installed.

 

If you have California emissions car, upstream is the more expensive heated AFR oxygen sensor. Shows exact fuel ratio, variable voltage. Car you have an additional AFR relay up front by the radiator.
Fed emissions was narrow-band oxygen sensor, only shows lean or rich - 1v or 0v.
O2 = oxygen. They're both "o2" sensors, one is narrow band one is wide band.

Depending on which scanner you use, the scanner could be displaying things in different, calculated values. So don't just assume one thing or another based on scanner data if you don't fully understand things.

 

Okay I think I got the car fixed. I found a
Technical Service BULLETIN and I got a pcm from the pick and pull. Took me a while to find the one I needed but so far so good. It says to do injector too but I didn’t. I’ve but about 300 miles on it and no light so far.
The STFT and LTFT are staying-3 to 4%
Thanks everyone for the help. I’ll see if I can post pics of the bulletin for maybe someone else with this issue.

 

Okay I think I got the car fixed. I found a
Technical Service BULLETIN and I got a pcm from the pick and pull. Took me a while to find the one I needed but so far so good. It says to do injector too but I didn’t. I’ve but about 300 miles on it and no light so far.
The STFT and LTFT are staying-3 to 4%
Thanks everyone for the help. I’ll see if I can post pics of the bulletin for maybe someone else with this issue. View attachment 405597
View attachment 405596
View attachment 405595
View attachment 405598 View attachment 405595 View attachment 405597 View attachment 405596 View attachment 405598

Don’t know why it made multiples but there it is.

 

One more thing to check in my experience with Toyota products is pull the Mass Airflow sensor and make sure the wire (s) and air temp sensor are wearing a dust beard. ( Think Seneca Crane). The wir is heated and the current changes necessary to maintain the wire current is how it measures the airflow. The beard is insulation. Easily cleaned with Windex or a spray bottle of rubbing alcohol and a gentle cleaning with a small hobby type paint brush. Or blow $15 on MAF cleaner. I saw 4 out of 5 fuel trim problems be the MAF. And 4 out of 5 of those cleaning did the trick. The rest split between the AFS and a vacuum leak. PS We used to order 3 MAF from the parts store so we would find a good one. Sport for OEM on Rock or your fav .com. Also very rarely the downstream O2 on the cat goes and skews the LTFT. The downstream is also used for fuel ration correction. Quick way to check MAF is disconnect it for a couple of days or a few drive cycles and see if the fuel trims correct with the ecm using AFS only. BTW +/- 12% is the normal range. Ideal is +/- 7%

 

Cool deal thank you for that. I’m trying to learn all I can. It ended up being the ecm, so far so good after today it should have about 500 miles on it and no light on. Long and short Trims seem to stay -4 to positive 4. I found a old service bulletin from Toyota telling about a random misfire p0300 that would not go away. Afterchecking everything I could and everything was in spec I did what it said.
I didn’t change injectors because they where not leaking and where in spec with wiring and fuel output…but I keep getting rich fuel trims no matter what.
Crazy thing is if the light where not on you would never know anything was wrong, it runs great

 

I thought I would throw that in for anyone else reading this. Clean the MAF once a year or once a month with a KN filter....I personally never replaced and ecm for a fuel code. Corollas and Matrix/Vibe for my car won't shift into drive is another story. The P0300 was likely a program change that made it harder for the light to come on. Still rough cold, but no light. And lastly, 100 things can turn on the light, very very few are something to leave you stranded. Glad it's fixed.

 

Why is everyone going on about the MAF? The OP stated the engine is 5SFE, which does not use a MAF, but rather a MAP, which is not the same thing and does not require any kind of cleaning. C'mon, people...

More and more threads these years where ECU ended up needing replacement. As these cars get close enough to be considered historical vehicles in many states, the old ECU's start biting the dust.