03 Tacoma P0171 code help

I have a 2003 Pre-Runner 2.7L 4 Cyl and my engine light came on recently after what I thought was initially a misfire but the code read "P0171". After googling it, I found that it could be the MAF sensor or the PCV valve. I replaced both. After replacing both I tried to test drive my truck down the street and it felt like it had no power and as if it was going to stall out even though it's an automatic and while driving it was making the sound as if it were cammed. I'm not sure what else to check for or replace so if anyone has any info let me know.

 

What your engine is experiencing is a low fuel - air ratio -- not enough fuel to match the amount of air, or too much air. This can be caused by a vacuum hose or gasket leak.

 

how would I check either of those things?

 

Good info for checking/diagnosing vacuum leaks:

https://youtu.be/qTzDY95aqXg

Diagnosing P0171 codes:
https://youtu.be/SugtR4KMIDU

(air/fuel sensor- located nearest the engine, “upstream” on the cat)

[p0172 codes are o2 sensor- located nearest the exhaust end of the cat, “downstream”, looks just like the other one, but they’re not interchangeable]



EDIT/UPDATE:


WELL..... my info was incomplete on the P0172 cause.... so now that I know that, even though your problem was the P0171...I still figure I have a duty to come back to this post and fill the gap there, just don't feel right about it any other way...

AS IT TURNS OUT... P0172 codes can also be related to MAF sensors, but it also appears that the cold AI filter can potentially be a cause as well as fuel injectors and fuel pressure regulators... If I can create a thread I'll do so but it'll be directly relating to P0172 as it applies directly TO that code. Conversely, if I CAN'T create a thread, I'll find another thread that specifies P0172 in the title and post the info I've collected as well as links in order to share the wealth... I hope it's forgivable, I'm still new to all this and have only been teaching myself through Haynes Manual, trial, error, TacomaWorld, and YouTube.... Sorry about the incompleteness of the information previously.

 

You can alternatively use wd40 in place of carb/choke cleaner with the same results, in case you didn’t know already…

 

Did the "no power" symptom occur only after you replaced the MAF and pcv?

What brand MAF did you use?

 

Or rather than using something which can harm other components in the engine bay, unlit propane can be used. Whatever you do- don't use brake cleaner.

 

Did not know that. Thank you

 

Ya know, the goofy thing is that it sounds like UR pickemup is behaving exactly like Tuesday (my 99 2.4L) I’ve been chasing p0171 & p0172 for a couple months now and I’ve replaced the PCV, the injectors, fuel filter, sparks, the crank position sensor, and both the o2 and air/fuel sensors, cleaned out my cat, double checked my air filter, cleaned out the throttle body, intake manifold, fuel rail, the EGR and the MAF … been all over the fuel intake and exhaust spectrum there’s not much else I can do but I haven’t yet hit up the TPS or the IAC and haven’t even looked sideways at the timing… lol … I just don’t know enough about it…
She turns over fine, idles fine, but getting her up to speed from a stop almost takes an act of God, she sputters and hiccups and hesitates and then eventually concedes to accelerating… and the fuel pump is fine… oh yeah, I’m not confident enough yet in checking the coil packs so I haven’t done those either…

 

Start replacing all the dry rotted and cracked vacuum hoses. So the EGR is functioning correctly? Hard start hot or cold? If all else fails try another ecuhttps://www.ebay.com/itm/165125508506

 

Either air leak on intake or vac line.......or its a bad maf or its wiring....

Nice if you could run live data....you could check maf readings at idle, and rev it and watch it....

If thats okay......high fuel trims would indicate intake/vac leak.....too much air getting around maf undetected....

And like previous poster said .....egr may be stuck.....

Another trouble spot there is a split or rotten pcv gromet....looks fine on top, but bottom is sliced off hanging, waiting to fall into the valves......massive vac leak there...

 

I've been getting a P0171 code for a while as well. I have until April to fix it when I need to smog my truck.

I have high fuel trims indicating a vacuum leak.

I bought a cheapy smoke machine on ebay. I'm fairly confident I have leak from somewhere on top the engine but can't pin point it.
I have supercharger and the smoke seems to come from the rearward part of the engine toward the drivers side.
I've suck a camera down there and sprayed everything with soapy water looking for bubbles while the smoke machine was hooked up.

I think but I'm not sure that this is a related problem but every now and then I can faintly smell gasoline. I replaced the injectors with rebuilt ones from motors west when I installed the supercharger 32,000 miles ago.

Could a leaky injector seal or leaky fuel rail cause a p0717?
Rather than a vacuum leak letting in too much air it's not getting enough fuel?

I'm thinking I might pull the supercharger off and go over the injectors and fuel rail in more detail.