P0171 wont go away

[Asoo]

Hi guys

I need your advice on this issue ,I drive a toyota Camry 2007 LE 4 cylinder with around 35,000 miles on it and I keep getting this error code P 0171 (system too lean ) my LTFT value is around 28 - 38 (which is way too high) , there are no drivability problems but it is slightly high in Fuel consumption and it does have a rough idle sometimes and is also slightly rough when on D and a hesitation/surge on acceleration.

this is what i have done so far

changed the MAF sensor
changed the air filter
changed the fuel pump
changed plugs
changed oil

checked for any vacuum leaks downstream the MAF and else where (none found)

pls guide me as to what else needs to be done

thank you all soo much


Also another issue I have is that , when I put my AT on D 4 it does not show up as 4 on the dash board but it stays on D and when i put it on 3 it is fine , so the 4 is missing / skipping ??? (it was fine when i had initially bought the car ie. when putting the gear on 4 it was showing 4 and when putting on D it was showing D )

[ELiTeCReW69]

check your pcv valve see if its clogged or damaged

[Asoo]

thx

could you pls tell me where the pcv valve is ?

[Jason.MZW20]

If you can't find a vacuum leak, then you most likely have an exhaust leak.

Any extra oxygen registered by the air-fuel ratio sensor will cause the ECU to increase the injector pulse widths to try and remove the oxygen from the exhaust stream. Some of the newer ECUs also trim off of the post catalyst O2 sensor. I know my CA spec 1MZ does.

[Asoo]

thank u

will check the exhaust for leaks and revert

[Asoo]

[ELiTeCReW69]

Once your looking at your engine (passenger side will be on your left and driver's side will be on your right) Remove the engine cover, and you will see a small little tube looking which its the pcv valve (its going to be in the back of the engine between engine & windshield on your left hand side) remove it, check if its clean & check if there's any damage on it.

Sorry I only answered you now =0]

[joshuaboston]

When I had that code P0171, it was my MAF sensor.

So my queston is are you using one from auto zone or did you buy one from toyota (denso makes it)?

Those MAF sesors are which you can buy from autozone are reconditioned and you may have bought a dud.... That's all I can think of.

p.s.
How expensive was it to change your fuel filter?

You are also due Per Toytoa to change your PVC valve... IT'S CHEAP... so just do it, but I doubt it is the cause.

Your car has 35K your warranty runs out at 36K... why don't you go to a dealership?

[greycamRy]

will this error code decrease engine life?

[Asoo]

@ Josh

The MAF I bought was from Toyota (Denso Make) and the fuel filter was a part of the fuel pump for which I paid around $300.

I wish I cud take it to a dealership but if u notice from my location there arent any dealerships in my area .

I will change the PCV valve and revert here

Thank you all soooo much for your input

[Jason.MZW20]

Well I had a nut come off on the rear bank exhaust manifold/pipe mounting area, and my long term fuel trims were +38% on the rear bank and I threw P0171 as it was just in range. I doubt that happened to you, but it'd be wise to check the exhaust manifold + gasket and any of the piping from the rear catalyst forward.

38% is the absolute maximum in either direction for short term + long term trims before you throw a rich or lean code.

[joshuaboston]

I still feel it's the MAF sensor... perhaps it the wiring harness. Buy brake cleaner and spray everything, check all wires on wiring harness. GOOD LUCK.

[Asoo]

I will check out the MAF sensor and the wiring , the PCV valve and will have them inspect my exhaust tomorrow at the shop .

thank you all

will keep u'll updated on the progress

[Asoo]

hi guys

A quick update

changed the PCV valve and inspected and cleaned the MAF sensor and checked out the exhaust ( it looks all fine)

Though the code hasnt been triggered off the LTFT is still around + 20 sometimes it drops to + 10 ....

I have noticed that the car rolls quite a bit before it starts , normally it shud start in one go but I could sometimes roll it twice before it starts esp if the car has been off for more than 10- 15 mins .

pls i need more advice

thx

[joshuaboston]

Originally Posted by Asoo

hi guys

A quick update

changed the PCV valve and inspected and cleaned the MAF sensor and checked out the exhaust ( it looks all fine)

Though the code hasnt been triggered off the LTFT is still around + 20 sometimes it drops to + 10 ....

I have noticed that the car rolls quite a bit before it starts , normally it shud start in one go but I could sometimes roll it twice before it starts esp if the car has been off for more than 10- 15 mins .

pls i need more advice

thx

I'm a bit of a noob...
But now you tell me it does not turn over right away.... is it your starter?

Maybe (long shot hear) there is moister between your coils and spark plugs... my wife's car had this problem (she has a subaru forster), she would get misfiring cyclinders... to fix this I put a generous amount of dielectircal grease on the tip of each coil housing. What is the moister level where you live?

I would do that, perhaps change the spark plugs, change out the engine's air filter... can't think of anything else.

GOOD LUCK!!!