[Xeio]

Hello again.
I have been battling a lean code on my mothers vehicle for some time now and i have run out of ideas. I have checked everything that i know to check (although i dont have a ton of experience with these cars specifically) The lean code appears under slight load at any engine temp. Idle is fine and car is not lean during idle.

Things that have been done are the following

replaced MAF and both upstream o2's -no change so we reinstalled the old sensors. Scan data shows all the sensors operating in normal range regardless.

tirelessly checked for vac leaks, i am 100% confident there are no leaks from any hose or from the upper portion of the intake.

replaced the upper intake gasket

replaced the PCV valve

ran many cans of seafoam through the tank

new sparkplugs

did a compression test, has great compression, so im leaning away from headgasket

the code is for bank 1 only so i moved bank 1's injectors and coils to bank 2 and vice versa.



After all of this, same code persists. Where do i go from here? My mother is seriously debating trying to sell the car as is which i have convinced her not to so far.

I read that if cam timing jumped a tooth, it could cause a lean condition. Is it hard to check the cam timing on these engines?


Whatever suggestions anyone has, shoot them this way. No matter how redundant it might seem, i am willing to try anything at this point.

 

[new echo owner]

Not very like timing jump causing lean running, but you can check cam timing by putting engine at TDC, remove upper timing cover to have a look!

Just curious, why didn't you put the AF sensor on bank 1?

 

[eherlihy]

I had a similar code (P0174 - Bank 2 [front] lean), and fixed it by replacing the O2 sensor.

Note that there are 2 different Toyota part numbers for the primary (before the cat) O2 sensors, and the difference is 2½" in the length of the wire. The shorter one is too short to fit where the longer one is needed. I don't remember which is which. However, there is 1 Denso part number, 2349021, and that one is long enough to work for either bank.

 

[Xeio]

Not very like timing jump causing lean running, but you can check cam timing by putting engine at TDC, remove upper timing cover to have a look!

Just curious, why didn't you put the AF sensor on bank 1?

Didnt see a point as the scan data was all in check.
I guess it's worth a try though, after the first 2 sensors didn't help, I learned how to interpret the scanners data and determined the sensors was giving normal data and seemed to be operating fine

I had a similar code (P0174 - Bank 2 [front] lean), and fixed it by replacing the O2 sensor.

Correct me if I'm wrong but does each o2 control one bank each?

 

[eherlihy]

There are 3 O2 sensors on the 1MZ-FE engine. One for each bank, and one after the CATalytic converter. The O2 sensors before the cat have a continuously variable output, based on the temperature of the exhaust gasses. The one after the CAT has a binary (on or off) output.

Also - DO NOT BUY O2 SENSORS from Amazon or eBay! - Many of them are counterfeits or returns. Get your O2 sensors from a reliable source, like your nearby Toyota Dealer or oempartsource.com.

 

[new echo owner]

Was just curious, since you already have it, why not see what happens!
BTW, do you have the sensors output voltage reading?

 

[Xeio]

However, there is 1 Denso part number, 2349021

I just bought the sensor. 200 freaking dollars! Going to install it right away

 

[yoyogi]

Hello again.
I have been battling a lean code on my mothers vehicle for some time now and i have run out of ideas. I have checked everything that i know to check (although i dont have a ton of experience with these cars specifically) The lean code appears under slight load at any engine temp. Idle is fine and car is not lean during idle.

Things that have been done are the following

replaced MAF and front O2 (on manifold) -no change so we reinstalled the old sensors. Scan data shows all the sensors operating in normal range regardless.

tirelessly checked for vac leaks, i am 100% confident there are no leaks from any hose or from the upper portion of the intake.

replaced the upper intake gasket

replaced the PCV valve

ran many cans of seafoam through the tank

new sparkplugs

did a compression test, has great compression, so im leaning away from headgasket

the code is for bank 1 only so i moved bank 1's injectors and coils to bank 2 and vice versa.



After all of this, same code persists. Where do i go from here? My mother is seriously debating trying to sell the car as is which i have convinced her not to so far.

I read that if cam timing jumped a tooth, it could cause a lean condition. Is it hard to check the cam timing on these engines?


Whatever suggestions anyone has, shoot them this way. No matter how redundant it might seem, i am willing to try anything at this point.

Rockauto typically has OEM sensors for a lot cheaper. Anyway, when buying a MAF always by OEM, never buy aftermarket.

 

[Xeio]

Rockauto typically has OEM sensors for a lot cheaper. Anyway, when buying a MAF always by OEM, never buy aftermarket.

if this fixes the problem i will more than likely buy a cheaper one from rockauto.


How does one remove the stupid grommet for the o2 wire? Is it even reusable? the new o2 didnt come with one.
I did some digging, none of the o2 on rockauto come with grommets. None of my local part stores have ones with it either. The only one I've seen are ones from Amazon for 50 dollars..

 

[ND Camry Owner]

@Xeio

Can you post some pictures of the engine vacuum hoses and the intake hoses? I know you said you checked them I would just like to see some pictures.

Have you checked the PCV valve hose? This hose with your year and mileage will give you a code and is very hard to see if the hose is split or cracked at all.

 

[Xeio]

Can you post some pictures of the engine vacuum hoses and the intake hoses? I know you said you checked them I would just like to see some pictures.

Sure, I will get some pics up later.
I didn't take the pcv hose off but it seemed okay. I will check.

 

[Wheatwacked]

ran many cans of seafoam through the tank

car is not lean during idle.

How do you know? How many miles?
Techron Injector cleaner works. It has a special ingredient that disolves the sludge. Every thing else is simple mixes of mineral oils.
When you swapped injectors did anything change? What are the long term fuel trims at hot idle? Should be varying from plus to minus 10%. Cracked bank 1 manifold or failed gasket? Or did the new sensor fix it?

 

[Xeio]

How do you know? How many miles?

FTs are within 10% at idle. car has 180k although 90% of the miles are highway miles.

When you swapped injectors did anything change?

Nothing changed whatsoever, car ran the same and eventually spit the same code. Same with coil packs.

Cracked bank 1 manifold or failed gasket?

the old gasket was deteriorating and cracking, which gave me hope. Replaced it with no change. I am unable to find any vac leaks near the intake whatsoever.
I havent been able to get the new sensor in, the car has been in use the past 2 days

 

[Wheatwacked]

If fuel trim is normal, then it is not a vacuum leak or restricted injector. What is the compression. These engines can have leaky head gaskets that leak between cylinders but do not involve the coolant passages and don't set codes. Had that in my Matrix. Come to think of it mine just slowly loss power as it got worse.

 

[BillDurham]

Can you look at the freeze frame and tell us if this code sets at idle or moving? And yes, I have seen a couple of P0171 Camry 4 cyl with the belt off a tooth. But only when it came in after someone else did the belt. And the complaint was my car just does not have the pep it used to and now the light is on.

 

[Xeio]

If fuel trim is normal, then it is not a vacuum leak or restricted injector. What is the compression. These engines can have leaky head gaskets that leak between cylinders but do not involve the coolant passages and don't set codes. Had that in my Matrix. Come to think of it mine just slowly loss power as it got worse.

all cylinders were around 150 or above.

Can you look at the freeze frame and tell us if this code sets at idle or moving? And yes, I have seen a couple of P0171 Camry 4 cyl with the belt off a tooth. But only when it came in after someone else did the belt. And the complaint was my car just does not have the pep it used to and now the light is on.

code is always set when under load. 30% or more. Car seems to run amazing, idles fine and doesnt hesitate or stutter. Only weird behavior is if you stab the gas in Neutral It will rev up slightly, hesitate a bit and even drop 100 rpm or so and then rev up normally. Maybe that could be caused by the vacuum surge tank i broke and then deleted? (this was after the code already appeared)

 

[Xeio]

finally got bank 1's o2 sensor replaced and the code returned...

What's odd is the car runs perfectly fine, no misses whatsoever and plenty of power.

I feel the need to check if the timing jumped a tooth but not sure where to start!

Can you post some pictures of the engine vacuum hoses and the intake hoses? I know you said you checked them I would just like to see some pictures.

I took a few pics but its honestly hard to make anything out. I am pretty confident all the lines are in the right places though

 

[Wheatwacked]

the vacuum surge tank i broke and then deleted?

That tank and its check valve is to maintain vacuum in the HVAC under different loads. Without it you might find the vacuum controlled doors open and close with the engine load. If one of the actuators is leaking it could be your leak. Replace the tank and checkvalve or at least block it off entirely to see what happens. That small leak may be slowing the response of the fuel pressure regulator or the regulator is failing. Does it hold vacuum? Low manifold vacuum = higher fuel pressure.

It will rev up slightly, hesitate a bit and even drop 100 rpm or so and then rev up normally.

. This is not normal.
Still could be clogged injectors. For $10 of Techron you might be surprised.

 

[Xeio]

I hope im not breaking rules reviving an old thread, if so, delete my post and i will create a new thread.

I managed to get the timing covers off and from what i can tell, the engine is timed correctly. Its kinda hard to see bank 1s camshaft mark but i took a video and everything seems to line up. Please watch the clip and let me know. VID_20230305_162824

Lets assume no vac leak, good compression, engine in time and fuel delivery is ok. What does that leave? ECU? Would it be possible that the ECU is detecting a lean condition when there is none? Ive said this before in these threads but the car runs amazing. Plenty of power and no hesitation or bucking. (other than the weird rev down and then rev up when stabbing the gas in Park) I will get a video of that when i get the car back together.


In fact, i am quite surprised just how quick this little car is when it downshifts.

Oh, my mother has still been driving the car and i noticed the new PCV valve i installed is leaking quite a bit, is this relevant?

Still could be clogged injectors. For $10 of Techron you might be surprised.

If it were the injectors, the code should have swapped to front bank right? (i moved rear injectors to front and front to the rear.) Same code.
Also we have run a couple bottles of fuel injector cleaner through it already.

Replace the tank and checkvalve

where is this check valve you are referring to?

 

[Wheatwacked]

somewhere between the manifold and the tank. It may have been removed or could be built into the tank itself. find a vacuum diagram. What injector cleaner? Once you have the injectors out anyway, you can test them with a 9 volt battery and a spray can of carb cleaner and a rubbber nipple. Watch the spray patter. Wear eye protection.
What are the LRFTR and STFTR?