First of all.. a code simply stating that the O@ is lean, or rich does not automatically mean the sensor is bad (and replacing it will fix anything). It may be good, and simply reporting what it truly sees: a rich, or lean condition.
Now:
Let's list common causes for each code, and see if we can't find a culprit for them
0133
HO2S Sensor Circuit Slow Response (HO2S-11)
(rich to lean switch was over one second in length.)
0171
Fuel System too Lean
bank 1
0174
Fuel System too Lean
bank 2
1131
Lack of O2 1-1 switches, Sensor at lean limit.
So...
Everything here states that you are running incredibly lean.
(including the switch rate, because, DING: you aren't switching.. it's staying lean all the time.
Now.. Common causes:
0133
Contaminated Sensor
Shorted or Open wiring
Improper Fueling
Faulty MAF sensor
Exhaust Leaks (just before the sensor, allowing fresh air in the mix...)
Inlet Air Leaks.
1133:
LONG LIST
Electrical
- Damaged O2 sensor (1-1)
- Damaged PCM
Fuel system
- Excessive fuel pressure
- Leaking/Contaminated fuel injectors
- leaking fuel pressure regulator
- Low fuel pressure, or running out of fuel
- Vapor recovery system
Induction system
- Air leaks after the MAF
- Vacuum leaks
- PCV system
- Improperly seated engine oil dipstick
EGR system
- leaking EGR gasket
- Stuck EGR valve
- leaking diaphragm or EVR
Base Engine:
- Oil overfill
- Cylinder compression
- Cam timing
- Echaust leaks before or near the O2's
Now.. of all those causes.. the common ones are?
MAF sensor, air leaks, and exhaust leaks.
Check your EGR vacuum tube (green vacuum tube on top of the EGR.. careful, it will be BRITTLE and can snap.)
Make sure it is still pressed on top of the EGR nipple, there are no cracks, or splits, and that the rubber boot is still good. I wouldn't look at the EGR valve itself, as a failure there is very unlikely, but a leaking gasket (how old are the gaskets on there, anyway?) can cause the same thing.
Check your air induction system.. I would give you model specific advice, but I can tell that you failed to read the FAQ and the post that says "newbies: READ ME BEFORE POSTING!!" It states to give mileage, year, make, and model with EVERY troubleshooting post, to help us give you tailored information. Try doing that from now on.
Anyway.. in general terms, look for split rubber hoses, or perhaps a disconnected tube. Leaking TB gasket, or UIM/LIM gaskets can cause this as well. Basically any air getting in to the engine after the maf.. (all air should enter and be measured by the maf.. anything else throws off the calulations...)
So.. to reiterate:
start simple:
look for vacuum leaks, vacuum tubes broken or cracked, etc.
Look for gasket leaks, or air induction leaks.
then move to more extensive things such as the MAF, or injectors being faulty. I HIGHLY doubt this, though, so KISS (keep it simple..add your own last word, for your own uses..) If all else fails, the PCV valve is incredibly cheap, but would require you to remove the UIM to get to it (would be a GREAT reason to, as well.. it SURELY needs cleaning!!!)
As a tip: try spraying carb starter spray in different areas with the car running (avoid letting it go in to the air filter, though), and see if the car stumbles or studders at any point. Whenever it does, you have found a minute crack that lets the spray in to the engine, causing studdering... there's your culprit.
Lastly: if you plan on keeping this car, contact Todras and purchase a Ford Factory CD from him (I think it is either 8, or 9 dollars SHIPPED, and contains enough info to tear down and rebuild the entire car!!! (body, engine, everything..)
Anyway.. hope that helps.
Ray
