Please for the love of God. Bank 1 and 2 lean codes.

2014 5.7 167k. I'm struggling folks. Checked over and over again for vacuum leaks. Sprayed both carb cleaner and propane.

Replaced/checked the following:

New OE MAF.
PCV valve.
Wix air filter
New OE purge solenoid.
Cleaned throttle body.
New Denso upstream O2 sensors

Long-term fuel trims are +28-30% at idle and +35-38% at 70mph.
I have no noticeable drivability issues other than decreased fuel mileage. No hard/long cranks (lol). No hesitation.

*Update 3/6/24. This truck went to a Toyota only shop for a week and they diagnosed it with a weak fuel pump. They replaced it. It did not solve the lean codes. They are at a loss. I replaced one bank with remanufactured injectors. No change. I am considering trading this in for a F150 at a considerable loss

 

O2 sensors

 

Yes, I thought about disconnecting both sensors on one side, driving around and seeing if fuel trims level out. It seems weird to me that it wouldn't have a CEL for o2, if one were bad.

 

I believe he is talking about your sensors being bad and cleaning or testing them for proper operation with a possible replacement.
It can happen but weird 2 primary O2 sensors are bad.
If you disconnect them your ecu will be in default mode, limp mode and run like crap. You won't get a definitive outcome of what's going on.
What codes do you have? We're you able to spray your intake runners to see if it increased rpm for a leak?
Both banks would mean an air leak, vacuum leak that will affect both banks. All hoses connected? No cracks or splits. When spraying use the red straw to direct at each component.
Good luck

 

P0171 and P0174. I've sprayed probably two cans of carb and choke cleaner on every thing in sight. It also sits and idles perfectly. I've looked at every hose and line I can think of. And if it were an external vacuum leak I would expect it to get better at cruising speed. That is just my speculation.

 

Are Vacuum boosters for power brakes still a thing? Can you hear or feel any difference when you apply the brakes?

 

I've looked at a lot of the wiring, I see no evidence of rodents. That doesn't mean they haven't been someplace I can't find.. I've read about other people getting a vacuum leak from the brake booster. I don't get any kind of surge If I apply the brakes.

 

If you had low fuel psi I'd suspect at least a misfire code. Stinks it's only these codes...
Can you hook up a vacuum gauge and see if its erratic?

 

I usually have good luck using maf cleaner and it evaporates quickly.

 

At idle is where you might see it. Reason I mentioned it is because I had a booster diaphragm crack (not on a Tundra) and I had similar problems. You might try using an unlit propane torch for troubleshooting as todays carb and brake cleaners may not be flammable....Unless you are sure they are.

 

Right, yeah I would expect more symptoms of low fuel pressure which I am not getting, so I'm hesitant to just blame it on a fuel pump and have to drop the tank. I am unfamiliar with a vacuum gauge. But I will look into that

 

Right, if I press the brakes at idle, I get no difference. Even looking at the RPM live data. I also fogged that whole area with propane a couple weeks ago.

 

How did that throttle body gasket look? Got a good seal? Cracked intake, not likely?
Take the fuel regulator out and see if it clean or gunked up. Just throwing ideas out there I've chased my share of unwanted air intrusions...

 

Throttle body gasket and intake all look good, and I've squeezed and sprayed them. Fuel pressure regulator is next I suppose. I wish there was a simpler way to test fuel rail pressure on these trucks.

 

There are adapters you can attach from regulator to quick disconnect hose. You have to search but that one fitting I used for my fuel system. They have other styles you can make with a psi gauge. Search for 5/16 quick disconnect fuel fitting. Some auto stores have them too.

$10 EVIL ENERGY 6AN Male to 5/16" SAE Quick-Disconnect Female EFI Fuel Rail Fitting

https://www.amazon.com/dp/B07FK7Y6P...2V0TmFtZT1zcF9waG9uZV9kZXRhaWwp13NParams&th=1

https://www.amazon.com/dp/B07FK7Y6P...2V0TmFtZT1zcF9waG9uZV9kZXRhaWwp13NParams&th=1

 

Yeah I've looked into rigging that up. I am away from home, but I suppose I will order those and do it when I get back. My fuel pressure regulator doesn't seem to be gunked. And the vacuum line doesn't smell like fuel as if the diaphragm were bad.

 

FFV or non FFV?

 

Non-FFV. Atleast as far as I can tell. No badging and my gas cap says "no E85". I've been at altitude a lot but have still avoided ethanol.

 

What do you think is measuring the lean condition thus triggering the code? Your O2 sensors. Had this problem with my wife's H6 Subaru. 02 sensors fixed the issue. I don't know if they got corrupted with bad gas or what, but swapping them out permanently cleared the issue.

One other thought, have you considered bad gas? Also, you could put in a heavy dose of fuel injector cleaner with fresh fuel and go beat on it for a couple hours, hold it in gear at higher revs? May clean things up and clear things out. At a minimum, it will be a couple hours of fun ;-) These motors LOVE to rev, and make fantastic sounds.

 

Another vote for replacing at least one O2 sensor to see if it fixes one bank. Assuming they're the same O2 sensors on each side, can swap it and see if the problem transfers from side to side.

 

O2 sensors don’t have to overtly fail to become less efficient. I’m leaning (no pun intended) towards O2 sensors being the culprit here.

 

Yeah, funny you mention. I was about to pull the trigger on both upstream o2s, but I started putting Lucas-oil fuel injector cleaner in the tank over the course of about 800 miles today and my MPG returned to something bearable and my long-term fuel trims started to slowly come down. I still might replace o2 sensors, as I'm assuming they are original. These 5.7s do love to rev. Tow haul on and 4hi in the sand is a blast.

 

New O2s. No dice. +30 fuel trim like clockwork

 

Did you ever find a solution?

 

Yeah actually. I got a used ECM from an auto recycler locally and then sent that out to get reprogrammed for my VIN. 300 bucks total and no codes. Go figure