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05 mustang gt p0174 code

5K views 9 replies 5 participants last post by  JKrew 
#1 ·
I recently bought this car and it was driving fine. The check engine light came on and said that bank 2 was too lean. I’ve replaced the Maf sensor, fuel filter, bank 2 sensor 1 ,02 sensor and the light is still on. I erased the code but after about a day or two it comes back . I recently hooked a scanner up to it and the LTFT For bank 2 was at +25.00 and the STFT was at + 2.30 and this was at about 753 rpm. Ive ran a smoke test and couldn’t find anything. Any help or advise would be appreciated.
 
#2 ·
What's the history on the car. Is there an aftermarket CAI?
Was or is the car tuned?
What, if any performance modifications have been done.
 
#3 ·
Since the lean code is specific to the left (driver's side) bank, make sure the O2 sensor wiring on that side isn't pinched or frayed as it could be shorting out. Also check if there's a leak at the exhaust manifold gasket or, if you have headers, at the collector.
 
#4 ·
So everything on the car is stock. When replacing the 02 sensor I made sure all the wires were properly connected and I also put wire loom around them. As for the exhaust manifold I replaced the gaskets with the metal OE ones and I can’t hear any exhaust leaks. I was hoping it was a vacuum leak, but when running a smoke test there wasn’t any leaks except smoke coming out of the entrance of the air cleaner box.
 
#7 ·
I actually suspected the fuel injectors so I added a bottle of Lucas fuel injector cleaner and later on that day the light turned off, but it turned back on the next day . So I think I might replace the fuel injectors. And the LTFT on bank one was a 17.2 and the STFT was at -5.5 and this is at idle
 
#8 ·
my car had the same issue and it turned out to be a loose timing chain - it is at the dealership being fixed right now... i did the same as you - MAF, O2 Sensors, fuel filter, fuel rail pressure sensor, etc. and still couldn't keep it from coming back. my short and long term fuel trim readings were way off like yours. i even put injector cleaner and fuel treatments too. then i admitted defeat and took it to the shop.
 
#10 ·
That's interesting! I have a slight timing chain rattle (ever since I messed up let the car get too low on oil) and my fuel trim have been slightly high, but not enough to throw a code. I always thought the fuel trim was due to having a BBK no tune CAI, but based on what you are saying I wonder if it is related to the timing chain which I've just been putting off fixing since that's a little more complicated job.
 
#9 ·
A loose timing chain (usually caused by worn guide or broken tensioner) will produce an audible rattle at low rpm so it should be fairly obvious.
The LTFTs are positive on both cylinder banks indicating that the engine has been running lean for some time, with the ECU trying to compensate by raising the injector duty cycle.
Since the injectors are 15 years old, it's probably a good idea to replace them anyway. Even if they don't completely solve your problem, the engine will probably still run better and deliver improved gas mileage so it'll be money well spent.
 
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