Need some help... P0171 Code coming and going

[ClassyJalopy]

What's interesting in your case. Is only the P0171. Even though I suspected fuel starvation. Typically I'd look for both bank 1 and 2 (P0171 & P0174) to indicate a fuel starvation issue, due to fuel delivery. I'm confident the fuel pump and filter did solve your issue, at least enough. But I suspect you've more to consider.

You said "Fuel injector cleaner (part of my regular PM)". Consider sending to someone like FIS. Also consider replacing fuel pressure regulator, considering mileage and your MPG drop.

When to Clean or Replace fuel injectors

Please post your experiences and thoughts on the subject. I’ve been considering cleaning or even replacing all 8 fuel injectors, is this wasting time and money. I understand keeping fuel injector clean by adding a can of additive to the gas tank, now & then, is a good practice. This keeps them...

forum.ih8mud.com

I did not see you mention spark plugs.

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

This is good food for thought for me. I have a new fuel filter and newish fuel pump and still can't kick the P0171. I also have fresh plugs!

 

[2001LC]

Also look for vacuum leaks. This includes intake manifold (IM) gaskets and the seal at base of fuel injectors in IM.

 

[ClassyJalopy]

Also look for vacuum leaks. This includes intake manifold (IM) gaskets and the seal at base of fuel injectors in IM.

My search-fu must be weak! Is there a write up for the fuel injector seals?

 

[2001LC]

You see some info here on FI for VVT engine. Scored 2006 LC w/194K AHC (untouched Jewell restoration) The 98-05 non VVT FI have addition seal at top into fuel rail IIRC.
Use your VIN # to order parts insures you get the correct ones.

 

[knewstance]

My P0171 code has not returned.

Just to check up again, still hasn't returned after a few months?

 

[2001LC]

Just to check up again, still hasn't returned after a few months?

What all did you do "a few months" back to correct?

 

[KFunk740]

For others looking for what to do about P0171:
I can't stress this enough, but learn how fuel trims work, and look at your STFT and LTFT while driving, before throwing parts at it. Just google for lots of explanations. Bootlegged toyota techstream will tell you the FTs, but its a hassle to use on a laptop, and I found it easier to use some free program called ‘car scanner' I think and looked at 'all sensors' with my ipad and the cheapo elm327 reader.
I have a whole thread about it, but I found that the P0171 was actually lying, and I was really lean on Bank 2 instead, but only under load. I then checked Bank 2 upstream sensor, and found it loose in threads. Went ahead and used a new sensor while I was under there, got it in tight, and all fuel trims were back normal and CEL is not coming back.

 

[REZARF]

No issues or codes since fellas.

 

[ToyotaTechnical]

For others that maybe battling P0171- Do not start throwing parts at it.

Find the fuel delivery issue, or the vac leak. Smoke test can be a huge help, especially if they have die infused smoke.

I have been looking for this vac leak for many months - turns out the injector grommets were cracked. This seems to be rarely mentioned, but becoming more common as the vehicles age.

LTFT were at 20% at idle for both banks. After new injector grommets- LTFT are at 6%. Much better, but not perfect.

Injector grommets can be replaced without pulling intake manifold. You just have to loosen the 4 fuel rail nuts on top, the 10mm bolt on front of intake, and 2x 10mm bolts on rear of intake.

Here are the old grommets. The new injector grommets are not an identical match to the shape of the originals. There has been a design change or supersede over the years.

8x, Fuel Injector Grommet: 23291-41010

 

[ClassyJalopy]

For others that maybe battling P0171- Do not start throwing parts at it.

Find the fuel delivery issue, or the vac leak. Smoke test can be a huge help, especially if they have die infused smoke.

I have been looking for this vac leak for many months - turns out the injector grommets were cracked. This seems to be rarely mentioned, but becoming more common as the vehicles age.

LTFT were at 20% at idle for both banks. After new injector grommets- LTFT are at 6%. Much better, but not perfect.

Injector grommets can be replaced without pulling intake manifold. You just have to loosen the 4 fuel rail nuts on top, the 10mm bolt on front of intake, and 2x 10mm bolts on rear of intake.

Here are the old grommets. The new injector grommets are not an identical match to the shape of the originals. There has been a design change or supersede over the years.

8x, Fuel Injector Grommet: 23291-41010

View attachment 3186433
View attachment 3186434

Smoke test is a great advice. Mine was caused by the aftermarket intake gaskets put on by a careless shop when they replaced the started for my old 98.