Lean code, but this one's hard

Did you check for any exhaust leaks? That's what mine wound up being.

 

Yeah definitely check for this. Didn't the 2.7 and 2.4 have a cast manifold that likes to crack?

 

This is a very solid response, I also suspect your intake, could be causing incorrect airflow and throwing off the MAF. Sometimes the fan can blow light air into the cone style cold air and small amounts of un metered air bypassing the tps can do this and confuse the maf, and remember MAF is king in an automotive system.

 

Oooh good catch. My wife's 96 did that.

 

Yep. He could either get someone with a MIG welder to repair it, or even braze it himself, but alot of people really like those Doug Thorley headers.

 

Ok so heres what i got to...

The vacuum line for the FPR doesnt jave proper vacuum, but when proper vacuum is applied the running fuel pressure is within spec. About 35 psi. However the pump doesnt turn on when the ignition is set to on, but this truck has been ghetto wired by some asshole before so i think thats why. But anyway, with the new pump, filter, and supposedly proper FPR function, as well as the LTFT symptoms, im going to shell out the 450 for new injectors and keep my fingers crossed. Ill let you guys know...

 

I had a P0171 that took forever to figure out, for me it turned out to be a vacuum leak on the back of my supercharger. But the mechanic that was finally able to diagnose it told me that 95% of the time you get a P0171, it's because of a vacuum leak somewhere. Less common cause could be an exhaust leak or bad/dirty MAF sensor.

 

The line to the fpr isn't supposed to have any vacuum on it. It's a filtered supply line that just measures your atmospheric pressure to maintain 43.5psi

Also the fuel pump shouldn't engage until it's in IG2 (start) position.

It won't be a vacuum leak as the LTFT gets higher as the RPMs go up. Vacuum becomes less at higher rpm so the LTFT would drop without exception. Bad fuel pump, or dirty injectors, or bad exhaust leak, (cracked manfold, which you never addressed) janky "CAI" (did you replace with stock box yet?), or a bad or miswired MAF (pin locations did changed though the years on 5vz, I'm assuming 2rz did too)

$450 for injectors????? Wow, ok, your truck your money. I wouldn't changed them until you've checked your fuel pressure properly.

 

It'll be super funny to me if after he threw all these parts at it, it wound up being an exhaust leak.
I mentioned that to him because I threw SO MANY parts at this code before it was solved.
My old Pre-Runner did run great after all that, though. Lol

 

Hey, update.
I was testing fuel pressure based on what the Haynes manual said to do, and it was pretty detailed. Long story short the fuel pressure and regulatory were both ok. I threw new injectors in because at that point with all new sensors and ok fuel pressure, as well as the LTFT symptoms, that it was possible enough. I have a friend that works at autozone, so it's really no money lost I can return them and just part swap all day, it's just kind of a pain in the a$$. Anyway, it didn't work (I'm sure your all very surprised... lol not) so anyway, I guess left on the chopping block is possibly cracked exhaust manifold, the ECM?
I took vacuum off the power steering pump using a T fitting to the FPR, I guess your saying I should just put it back? The Haynes manual says it should run between 32 and 38 psi at idle, I was closer to 45-48 until I put the vacuum on the FPR, then it came down to about 35 psi.

Can someone please give me some advice on how to check for a cracked manifold, I have no idea where to start other than looking and it's not visually damaged

 

You need to find a shop or someone that has a smoke machine to inject smoke into the intake and the evap system to find that leak. Also trash the after market CAI and go back to stock.
Also, a bad PCV will cause a lean condition.

 

The easiest ways are to spray the exhaust with somewhat soapy water and look for bubbles with it running, or have a friend hold a damp rag over the tail pipe while you look for leak(s).
Or just take it to a shop. Hell, get a new performance muffler put on it while you're there for poops and giggles.
And yes, replace the PCV valve. Easy to do and should cost you around 5 bucks.

 

You should be able to hear an exhaust leak.

 

Following, as I am getting this code as well.

 

When the code is set it should log the data at the time of malfunction. Have you ever looked at the log file?

 

Ok guys, next update. Factory intake reinstalled, new pcv valve, no effect whatsoever. Same conditions. Also we inspected the exhaust manifold, there are no cracks or damage pre cat. No leak until muffler clamp, which doesnt matter.
If it means anything to anyone, when we put brake cleaner or propane on the fikter while running to richen the mixture, the trims all adjust as expected. (Short term esspecially, and slowly long term) It starts to go negative fuel because it realizes its getting plenty.

But yeah, not exhaust leak or PCV or Intake issue.

 

Weird man. You already verified your O2 sensors are the correct part number for your model of taco, right?
And I'm not trying to be a putz, but the plastic intake tubing, etc is all good? Even a hairline split anywhere can cause your problem. I've seen some hairline splits in the accordion part that weren't even visible unless you removed the tube to look for it.

 

??

 

Im not sure how to check the log file, and what should i even look for? I have an obd2 reader that pulls live data, what do you want me to provide, if you guide me ill try to get it.

And yeah theres no damage to any part of either intake. And remember the fuel trims get dramatically worse as the rmp goes up, which rules out any kind of vacuum leak.

I ordered a computer. It will be in the 14th programmed for my truck... will let you guys know.

 

What type of scanner and software are you using?