toykidd

hey guys im have a bit of a problem i have a 2002 t4r with a Spectre CAI and roughly 210k (most mods are in sig) and i keep getting this reoccurring CEL its PO171 (bank 1) system too lean so i did some research and have found that cleaning your MAF sensor could fix that so i went to the autoparts store and bout myself some MAF cleaner and cleared the code then about a day later the code came back so i cleaned it again and yet again a couple days later same code. so i figured the sensor was bad so i replaced it. and sure enough the code came back a few days later and now it comes more frequently. so i had heard to hard reset my ECM so it could calibrate to the CAI. Yet again today the code came back. SO i have heard of a few possible problems, i have been told that the airflow might exceed the built in parameters in the ECM causing the system to run lean, or that i could have clogged up injectors or bad injectors. so i am done throwing parts at it (shouldn't have done it in the first place) and would like some input to see if anyone else has had this problem or any tests i can do to find out definitively what the problem is.
cheers

WHAHAHAJR

Have you cleaned your air filter lately? If so how much oil did you apply to it. Remember oil should only be applied to the out side of the filter. And the excess needs to be wiped off. Too much oil from the CAI could be you problem.

toykidd

spectre claims their filter to be an oil free filter and i just recently cleaned it with an air chuck. and correct me if im wrong but if my filter was clogged wouldn't rich not lean?
cheers

WHAHAHAJR

Ok well never mind. What I meant was sometimes too much oil can get on the sensor. Sorry if I'm no help just a thought...

toykidd

anyone have any other suggestions??

mt_goat

The FSM says these are the possible trouble areas for a P0171:


Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor (bank1 sensor1) malfunction

Mass air flow meter

Engine coolant temp. sensor

rworegon

FSM diagnostic for P0171 with a few more items than mt goat listed:

http://www.ncttora.com/fsm/1996/SIL/...e/cip0171p.pdf

toykidd

so what type of test can i run to check those systems i know how to check fuel pressure, but how can i test heated o2 and engine coolant temp and such?

enapa

Pull out coolant temp sensor and you can tell right away. It could have a bunch of deposits on it. I would run seafoam myself first. Half in fuel tank half through pcv.

mt_goat

That link posted by RW shows the diagnostics for the O2 (A/F)sensor (page 231), if you don't have the scan tools then you might try getting a spare sensor and swap it.

toykidd

if it is the o2 sensor it is the upstream sensor correct is there a different code for the rear sensor (post cats)?

mt_goat

The sensor #1 referred to in the FSM is the upstream sensor, the post cat sensor is #2. Both are bank #1 with these engines since they are not dual exhaust.

toykidd

update! so i ran a few tests checked fuel pressure and its sitting right at 50psi rechecked all vacuum lines no vacuum leak ran seafoam and checked ect sensor all those are in working order and still i have the code. so im about to run to the shop and see if i cant get a live scan of the o2 sensor so hopfuly we can figure it out!

enapa

Dont you need to reset ecu to clear code? Maybe you did this already, if so disregard.

toykidd

ok so another update i went to the local toyota shop told them my problem and they said that it is most likely that i got a bad maf sensor from advance auto parts and that i need a toyota MAF so i the toyota dealership and had them cross refrence the part numbers for the 2002 t4r MAF and the 2003 highlander (moms car) and they came back as the same part number so i went and switched the sensors and just my luck no code in the highlander and still got the code in my truck...(erased the code with the hand held OBD2 scanner) also yesterday i hooked up my car to the snap on modus scanner and it was showing my up stream A/F sensor was reading quite sluggish but still working. so if my upstream sensor was not working at all my car would get an O2 sensor code not a too lean code correct? because the upstrem o2 sensor tell me my fuel trim right?
please help im in desperate need!