Toyota Trouble Shooting

[bowtieguy]

my new(2001) corolla is throwing a P0171(lean) code. research leads me to ascertain that there's 1)a vacuum leak, 2)bad PVC valve or 3)bad MAF sensor...and a remote chance of having a bad O2 sensor.

i cleaned the MAF sensor, which makes the car run better, however the code comes back within 20 miles or so of driving. that leads me to believe there are no vacuum leaks(cannot find any anyway). the PCV valve still "rattles," so it is likely good.

so do i need a new MAF sensor? if so, here are my options...with advance auto coupons i can get a cardone brand reman with 1 year warranty for ~$50 or a new denso with lifetime warranty for ~$100.

what about the outside chance of needing an O2 sensor? other thoughts?

[JanGeo]

I would think you would want lean? However a reason you are running lean could be not enough fuel getting through the injectors from low fuel pressure or clogged injectors working so poorly that the system can not adjust enough to correct. Cleaning the MAF sensor resulting in better operation makes me think you nailed it though.

[GasSavers_BEEF]

on my dad's corolla, we replaced the MAF after a failed attempt cleaning. it still didn't take care of his issue. his issue isn't as critical as yours as his code will stay off for a while (at least long enough to pass inspection)

I am going to replace the upstream O2 sensor soon and see what happens. he isn't really worried about it since he recently got it inspected. I just want to fix it.

his is a 2006 but with 100k+ on it. it may be around 120k can't remember.

hopefully this fixes it and i found it cheap at rockauto.

[bowtieguy]

that reminds me...thanks beef...rockauto is having a close out on pre cat O2 sensor, beck/arnley brand, for 98-2002(i believe) corolla/prizm for $27.54 shipped. anyone owning a toyota 4 cyl may want to check this out for application.