Refurbished Fuel Injectors?

[LXKevin]

When my 02 lx470 was new to me i had the P0171 come on driving home from purchase. yay After many days reading here and studying the fsm. I changed pcv valve and hose, new factory MAF ( after cleaning original), cleaned throttle body, etc with no change in cel and code. One day when inspecting my vacuum lines (for the umpteenth time) for cracks i found my issue. It was a disconnected vacuum line from the power steering air control valve. Plugged it back in and have had no issues since. I was amazed that a tiny vacuum hose would introduce enough air to cause a lean condition. Long story short check all your vacuum lines and air intake housings for cracks or possibly a disconnected line. Good luck.

 

[abuck99]

Lean Condition- air leaking in somewhere or 02 sensor not working properly? As a part of the DI procedure for p0171, FSM specifically questions if the the vehicle has ever been run out of gas-.

What you can try with out TS, the easy stuff: check your air filter: clean & lid correctly sealed in place?, look at/trace all vacuum hoses & fittings- anything loose or broken?, disconnect battery (ground) for 15min and clean MAF- reconnect MAF and then battery, beyond that you'll need more in-depth diagnostic testing: you can test oxygen sensors for continuity: FSM has a procedure for that, you can look for exhaust leaks- might need smoke for that, you can check fuel pressure need vacuum gauge for that.

 

[KFunk740]

So about a month later I still haven't looked at the fuel trims and went on a 2000+ miles trip with p0171 still triggering the CEL !
I am far from home and finding my truck some times misfiring at low RPM when under load

I am heavily laden with 5 passengers and their stuff, so going uphill at highway speeds and starting off from a red light pronounces the misfire even more.

With no easy access to techstream what are my options for diagnosing this? I do have ELM327 wireless scanner with me. So I can read codes but that's abt it

You can see fuel trims with elm327, just need the right app. I found some generic sounding ‘car scanner’ free app, which has a bad interface, but gives you the numbers at least. You may have a fuel supply issue though, not sure if you’ve tried a fuel filter yet, and check underneath the car to make sure there are no leaks/drips.

 

[2001LC]

The advise with regards to vacuum leaks are great ones. Make sure you've none!

Additionally a field test for weak fuel pump may be worth a try. Pinch off fuel return line. If RPMs go up, it's a clue the fuel pump not putting out adequate pressure. Edited: Pinching could damage line!

The fact you only get bk 1 lean code only. Would suggest this is issue on bk 1. But not necessarily.
Some possible bk1:
Fuel injector to base of intake seal (grommet) leak bk1
Intake manifold gasket leak bk 1
Bad valve bk1
A bad cylinder(s) bk1
Exhaust leak bk 1
Weak O2(s)

Fuel return line. Wraps around back of intake manifold. Then hang on back of engine cover. The line going to fuel dampening device, comes from fuel filter and is inbound fuel main line. Do not pinch or kink fuel main line.

 

[ClassyJalopy]

Thanks guys. Just confirmed I don't have any missing or broken vacuum hoses. Here are other components replaced in last 2 or years
Fuel pump: 50k miles

25k miles old:
All plugs
All coils
Bank 1 o2 sensor 1
Fuel filter

10k miles old:
MAF sensor
Pcv and related hoses
Valve cover gasket
Spark plug gasket
Air filter

I will try the Car Scanner app to see of I can get the fuel trims

 

[abuck99]

Fwiw it's good practice to replace the O2 sensors together so Bank 1 Sensor 1 and Bank 2 Sensor 1. You might check the replaced O2 sensor is tight and not leaking exhaust to rule that out.

Curious when you replaced all those components (02 sensor, fuel pump, coils, MAF), did you use all OEM parts or OE family equivalent: Denso- Aisin- etc?

 

[ClassyJalopy]

Here's a screenshot of fuel trims. Engine in closed loop, transmission in drive and gas pressed to create engine load. At 1100 RPM with both front and rear AC on.
BTW I touched the bank one fuel injectors to check if there is any play in them or if the wire plug might be lose and didn't feel anything was out of order! BUT THE CEL WENT AWAY! Not sure if that is a clue for anything. This sceenshot below was taken while the CEL was off.

 

[ClassyJalopy]

Fwiw it's good practice to replace the O2 sensors together so Bank 1 Sensor 1 and Bank 2 Sensor 1. You might check the replaced O2 sensor is tight and not leaking exhaust to rule that out.

Curious when you replaced all those components (02 sensor, fuel pump, coils, MAF), did you use all OEM parts or OE family equivalent: Denso- Aisin- etc?

Coils are YEC Flamma, plugs and O2 sensor are Denso and everything else is Toyota OEM.

 

[abuck99]

Recheck the connector at the O2 sensor- remove ensure its clean and reconnect. Inspect wires. Also put a wrench on the sensor to ensure its snug. Fwiw grease from the front DS spider and yoke has a tendency to sling onto the 02 sensor- which can affect its performance.

 

[KFunk740]

Here's a screenshot of fuel trims. Engine in closed loop, transmission in drive and gas pressed to create engine load. At 1100 RPM with both front and rear AC on.
BTW I touched the bank one fuel injectors to check if there is any play in them or if the wire plug might be lose and didn't feel anything was out of order! BUT THE CEL WENT AWAY! Not sure if that is a clue for anything. This sceenshot below was taken while the CEL was off.
View attachment 2479787

I’m a little new to this, but looks like both banks are lean in the long term (probably when you put it under real load on the road), and I’m still betting fuel supply. Just hittin the gas in neutral isn’t going to simulate a load, you have to run it hard. When you drive it, you’ll probably see short term fuel trims go up, eventually until it sets a new long term fuel trim.
Single digit FTs is what you want, as it gets up toward +20, that means it’s overcompensating by 20 percent more fuel to try to get it right, and it’s still failing, so it’s triggering the light. Since your STFTs are fine in neutral, I think we can rule out vacuum related stuff. Most of those issues cause a problem at idle, but disappear at speed as the rush of air fuel just overwhelms all vacuum leaks.
Things aren’t just all wacky, so it’s probably not sensor related.
Since it’s both banks, I doubt it’s a single clogged injector on one side. I’d be looking at fuel leaks, fuel pump/filter, fuel pressure regulator, etc. you may need to tee in a fuel pressure gauge to properly diagnose.

Edit: just realized you said it was in drive, not neutral. But still, 1100 rpm in drive isn’t much of a load. Give it a real run and you’ll see your fts go up.

 

[KFunk740]

To reiterate, long term fuel trims of 17 and 20 percent are way, way wrong. Should be like 5 or less. It’s driveable-ish, but if you don’t figure out why both banks are running that lean, you could be screwed.

 

[ClassyJalopy]

I think putting her in drive and keeping it stationary while raising the RPM would put it under the load.

Yes I am concerned abt the LTFT being nearly 20% but the STFT is actually negative! Not sure what to make of this- did my fiddling with fuel injectors actually addressed the issue temporarily so the STFT are now trending towards improvement?

If yes then does that mean I should start with replacing the fuel injector seals?

 

[KFunk740]

I think putting her in drive and keeping it stationary while raising the RPM would put it under the load.

Yes I am concerned abt the LTFT being nearly 20% but the STFT is actually negative! Not sure what to make of this- did my fiddling with fuel injectors actually addressed the issue temporarily so the STFT are now trending towards improvement?

If yes then does that mean I should start with replacing the fuel injector seals?

No, just in drive while stationary isn't giving you a real load. You can leave the app on while you go for a drive and watch. When mine was acting up, I had to take it out on the road and really hit the gas hard before the FTs would start climbing up to 20. Just putting around at 35mph wouldn't really do it.

yeah, I meant to go on about the possibilities that fiddling with things did. Yeah, maybe the idle STFTs had been high until you accidentally bumped a vacuum tube into sealing up tighter, then the STFTs corrected themselves, but it will take some more time for the LTFTs would correct themselves.
But you said you had real stumbling issues under load, that doesn't sound like a vacuum leak type issue to me. A vacuum leak might make it run rough at idle, but it should be able to put down some power still when you ask it. You were almost certainly not getting enough fuel when you need it.
Now as for injector seals, my experience is that if those are just the teeny tiniest bit leaky, you're gonna be pouring fuel all over your engine and running it onto the ground. I know, because I just screwed them up a few times. If there's a hint of a gap, that fuel blasts out. They don't just suck a little excess air. Besides, your issue is on both banks as well, so bumping an injector on one side isn't going to fix the other.
Now one thing you could bump that might explain things is the fuel pressure regulator and its vacuum hose. Thats the innocent looking little piece at the end of the fuel rail on the passenger side. I'm not sure how it works exactly, but I believe vacuum is used to adjust the fuel pressure, and if I'm understanding it right if you're lacking vacuum there then it may fail to adjust fuel your fuel pressure. Not sure if that could result in lean or rich condition, though.
You could've bumped anything that'd help fuel flow better, but I'm doubtful on the whole bumping truly solving the issue thing. Most any associated issue would result in dumping fuel everywhere, and youd know it.
But if you want to know if its truly fixed, then just drive it hard for a little bit and see if the FTs get back down close to zero. If they do, awesome, but I'd still want to know what I did.

 

[ClassyJalopy]

Ok, so based on this my next step should be to borrow a fuel pressure guage and check the pressure.
Any chance you would have the fuel.prssure regulator number handy? Is there one on each bank?
Also, I noticed the i take air temp is 104° , that is way off! Ambient temp was around 70° today. Does that indicate abad intake air temp sensor somewhere?

 

[MJK]

From FSM DI-147:

The fact that both banks are off by so much and pretty similarly makes me think whatever is likely impacting both banks. So, IMO that makes things like exhaust leaks, injectors and 02 sensors less likely because you'd need similar failures on both banks. I'd start with cleaning and checking the MAF just because it is easy. From SF-32:

From there, you'll probably be going on to fuel. Scope out bent/crushed lines first. Then check pressure. 'There is more info in the FSM section SF-7+, but you are looking for 38-44psi during priming and at idle. It should remain at 21PSI or more for 5 mins after engine stop.

Lots of good info in the FSM.

 

[KFunk740]

Ok, so based on this my next step should be to borrow a fuel pressure guage and check the pressure.
Any chance you would have the fuel.prssure regulator number handy? Is there one on each bank?
Also, I noticed the i take air temp is 104° , that is way off! Ambient temp was around 70° today. Does that indicate abad intake air temp sensor somewhere?

Well, next thing i’d actually do is to drive it a little and watch the FTs some more, just to get a better idea of what’s going on. If the FTs go up under heavy load only, you know it’s probably lack of fuel delivery. They could do something else wacky though. I’d also take a close look at that FPR and it’s vacuum hose and maybe knock it around a little. I’ve heard of them having rust caught in them, don’t know though.
I have not tested fuel psi on one of these myself, so mjk may be pointing you in right direction in manual, as it needs special fitting. I recall there being a recent thread on DIY fuel psi testing rigs to have on hand.
I do not know if that air temp could produce such a result, but worth looking into. I’m actually new to figuring out EFI myself, hah. I’m more of a carb guy.

 

[OwnerCS]

Well, next thing i’d actually do is to drive it a little and watch the FTs some more, just to get a better idea of what’s going on. If the FTs go up under heavy load only, you know it’s probably lack of fuel delivery. They could do something else wacky though. I’d also take a close look at that FPR and it’s vacuum hose and maybe knock it around a little. I’ve heard of them having rust caught in them, don’t know though.
I have not tested fuel psi on one of these myself, so mjk may be pointing you in right direction in manual, as it needs special fitting. I recall there being a recent thread on DIY fuel psi testing rigs to have on hand.
I do not know if that air temp could produce such a result, but worth looking into. I’m actually new to figuring out EFI myself, hah. I’m more of a carb guy.

Side note - I replace the FPR as a standard part of the "mid-life" refresh baseline for vehicles over 20 years and 250,000 miles. Not saying this is your problem though.

 

[ClassyJalopy]

Drove it around a little and noticed the fuel trims are really high at idle speeds. When driving around STFT go into negative and the LTFT quickly return to single digits. Is that an indication of vacuum leak, since it is happening only at low RPM?

@MJK thanks for sharing the parts of FSM, unfortunately it doesn't look like checking fuel pressure at the rail is as simple as hooking a pressure guage to a valve, so it might have to wait until I get back.

Idle

After driving around

 

[jerryb]

I was going to write what he wrote, and add intake air temp is normal and I watch o2 voltage at the same time. With a big load and without, with enough time for refresh rate and voltage peak and valley.

Yes sir leak at idle
Delivery pressure is normal if. IF your o2 voltages are correct after seeing them, and the correspond to throttle position and load.

Freeway throttle 100 percent on and off with time lapse. Should see less than .3 v closed throttle fuel cut and wide open throttle 100% around .8v

idle has the most vac and the most affect on pressure. More vac less pressure. It will rise if you remove the vac signal but you won't be able to see it on an analog gauge. Unless there is something wildly different on the 98-03 100. It's not a check in the 04-07 FSM to remove the vac signal and check pressure.

 

[KFunk740]

Yeah, that is looking better in terms of fuel delivery if that’s the FTs under load. Your stumbling could just be due the transition from the s***ty/leaky condition off throttle to the decent condition on-throttle. It’s maybe not able to adjust that quickly. If you’re getting decent FTs under load though, that is a better outlook for your reliability on this trip.
Now, finding that possible vacuum leak. Have you checked if your intake manifold bolts are tight? Go ahead and see if they’re snug. Anybody changed the starter recently and left them loose?
You can try to spray some starter fluid (a tad dangerous) around the engine bay and see if you can get idle speed to jump when you find a vacuum leak. You may need to unplug the MAF sensor to get it into open loop first. Beyond that, there’s luck and inspecting all hoses, or rigging up a smoke test. Or you know, just bump whatever you bumped before. I suppose it’d be possible for all of the lower injector o-rings to just have terrible rubber and leak vacuum. I forgot, the bottom ones shouldn’t be under a lot of fuel pressure, those top ones sure are though.