Lean code, but this one's hard

Ok, 1999 tacoma, 2.4L, 2wd. Runs lean. We've inspected for vacuum leaks, there are none. Replaced both o2 sensors, MAF, and fuel filter twice each on the off chance the parts had been bad (this is like 4 plus months now) replaced fuel pump and screen, have run 2 cans of seafood and one of royal purple through tanks of 93 octane gas on different occasions. It has a Spectre piece of shit Cold Air Intake but had that for about a year before this happened.
It all started after I believe I got bad gas, and drove 40 miles with it running like shit to get home.
We've tried everything, only things left are fuel pressure regulator, (fuel pump I believe is ok but can't get a running psi on it Cuz Toyota left no service port, but it's starting psi is about 80) injectors, or, someone has said there is a chance the ECU may be bad and sending false readings or communicating wrong. I have reset it overnight (both cables offor battery) and code has come back. What's everyone's thoughts?

STFT varies but is usually -5 to 5
LTFT is currently 20% plus. Whicj sucks....
Does anyone know what 1st gen o2 sensor readings should be(voltage)? B3cause i would love to have a baseline to compare to...

Thanks everyone

 

Don't know if my 04 v6 would be the same but i'll get them tomorrow. Possibly a plugged injector? All the plugs have the same color porcelain?

 

How do you know it runs lean? Have you gotten a code? What is the exact code, post it. I'm assuming you have since you have a +20 LTFT. Make sure you're getting the right o2 sensor- '99 was a transition year they started using wideband o2 in some models. Check your MFG date.. if it's after 6/99 it should be a '00... Also the 49 and 50 state truck were different for the 2.7/2.4L 50 state used wideband, 49 state used narrowband in '99 Check o2 sensor here http://urdusa.com/store/Denso-Produ....html?osCsid=dea1bd1c58b55c480288c7e358fb8c01

I do immediately suspect your crappy CAI... they are known to cause all kinds of issues. If your airflow over the hot wires isn't right you'll have some wacky things going on. If the diameter of the tube is even slightly larger or smaller it'll make a big difference. I'd honestly try to swap that out before any more troubleshooting.

You can check the fuel pressure. At autozone you can rent a kit that has a banjo bolt adapter that has a service port on it, so you can tape a fuel pressure gauge to the windshield while you drive. Weak pump will definitely do that, but again since you've replace it :dunno:

If it were an injector, you'd be getting a misfire code for a single cylinder, so doubtful of that.

FPR is ok if it's not leaking fuel from the top vent port.

ECUs are rock solid, suspect it last.

Lastly don't run any more seafood through your tank LOLOL

 

Hahaha, I thought same thing when I read the post. Autocorrect cracks me up at times.

 

Ok so the exact code is an 0171, system too lean. I really can't imagine it's the CAI because I had it for a year no problem before all of this started. I still have the factory intake, I may put it on to see, but don't think that's it.
I checked the mfg date it's 12/98 so it should be in that oder period.

 

50 state or 49 state? Should say on a sticker under the hood. Figure out if you've got the right o2 sensor.

 

I honestly don't know how to tell but here's the under hood info

 

That's a Cali truck. You need a wideband bank 1 sensor starts with 234-9xxx. See if you have the correct sensor installed.

 

Subbed to this brainteaser

 

I'm checking that link you sent me I don't see where any 2.4 L models 1999 call for a 234-9xxx anywhere

 

As of right now this is one of the sensors

 

It could be an issue with the EVAP system...

 

What RPM does your truck idle? Do you have an air leak somewhere post MAF. Inspect all your vacuum hoses really well. Spray a can of starter fluid around all your hoses and joints and see if you can make it stumble. Is your exhaust manifold in good shape, not cracked?

What RPM do you have +20 LTFT? If you raise the RPM to say 2500, what does the LTFT say? If it's much smaller it's a vacuum leak somewhere.

 

I don't think so. Care to explain how?

 

@Caligula had an article he posted a link to about lean codes. Maybe he can help.

 

Ok idle us anywhere from 660 to 680, usually steady just in that are. LTFT is about 17 at idle but hits 30-35 at higher rpm while driving. Ive chevked for vac leaks in thr past and havent found any but will try again. Thanks for your timr everyone...

 

Multiple partially plugged injectors? Weak fuel pump? Definitely not a vacuum leak if it gets bigger as RPMs rise.

 

Maybe.. like i said i think i had bad gas once but... how could it shit on eveything so bad, it had a new fuel filter at the time, and ive simce changed it again... idk man i cant figure this one out

 

http://www.engine-misfire.com/p0171/

I know when I worked on cars for a brief time in my life there were some components of the evap system that could cause a lean fault. Maybe a check valve has gone bad somewhere inside the evap system allowing the engine to continually pull unmetered air behind the MAF. I'm not familiar with how Toyotas evap system is setup compared to the European brand I worked on but they should be similar in design plus or minus a check valve/sensor etc...