[BigB227]

So I've been having this code pop up it awhile now and can't seem to figure it out
It's code P0174 system too lean.
I've replaced the fuel pump, fuel filter, cleaned the mass airflow sensor with nothing helping.

I'm goin to replace the PCV valve as well soon but if that doesn't fix it then I'm at a loss. Anyone else have any ideas??

 

[1996mustang]

Have u tried replacing the upstream o2 sensor yet? I have the same code plus one p0171 and p0174 and u can tell im not running lean im running pig rich however i still need a tune and i eliminated the rear o2s so i still have yet to replace my o2 upstream. Just an idea. It could also be a vacuum leak as well so look for that as well

 

[cliffyk]

P0174 has the same possible causes as P0171, it is however indicating that bank 2 (driver side) O² sensor is reporting lean.

As it is just one bank reporting this look for possible causes that would only affect one bank--this pretty much rules out MAF issues and intake leaks before the TB; leaving exhaust leaks. Leaks upstream of the O² sensor and close by downstream (up to 12" or so) will cause the O² sensor to report the mix is lean when it really isn't...

 

[BigB227]

Have u tried replacing the upstream o2 sensor yet? I have the same code plus one p0171 and p0174 and u can tell im not running lean im running pig rich however i still need a tune and i eliminated the rear o2s so i still have yet to replace my o2 upstream. Just an idea. It could also be a vacuum leak as well so look for that as well

Well I havnt replaced any O2 sensors but I do have a custom tune by Bama to compensate for my O/R pipe and 70mm throttle body and plenum

 

[98GTCONV]

I've got the same issue, I have some new o2 sensors to put on, once I do, ill let you know if it did the trick

 

[cliffyk]

Well I havnt replaced any O2 sensors but I do have a custom tune by Bama to compensate for my O/R pipe and 70mm throttle body and plenum

That has nothing to do with the front O² sensors, the ones used by the PCM to control the engine in closed-loop mode.

Also there is nothing that needs to be changed in the tune for an aftermarket TB and plenum--the MAF continues to monitor the mass of the air entering then engine, and the PCM adjusts things accordingly. The same tune changes that fix the stock tune's "suckiness" work just fine with any intake mod you might install..