Ford codes - http://www.obd-codes.com/trouble_codes/ford/
generic codes - http://www.obd-codes.com/trouble_codes/
Copied from their site:
P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2 http://www.obd-codes.com/trouble_codes/ford/p1151.php
P0171 System too Lean (Bank 1) http://www.obd-codes.com/p0171
# P0305 Cylinder 5 Misfire Detected http://www.obd-codes.com/p0305
# P0306 Cylinder 6 Misfire Detected http://www.obd-codes.com/p0306
put those links in your address bar for more detailed info...seems to me like you're not getting enough fuel?
the 1151 is the main cause of concern, the misfire codes are probably just secondary to that problem. Again, copied from the link:
System Too Lean (Bank 1)
What does that mean?
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.
Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
A code P0171 may mean that one or more of the following has happened:
* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
* There could be a vacuum leak downstream of the MAF sensor.
A code P1151 may mean that one or more of the following has happened:
* Short to VPWR in the harness or HO2S
* Water in the harness connector
* Open/shorted HO2S circuit
* Corrosion or poor mating terminals and wiring
* Damaged HO2S
* Damaged PCM
* Excessive fuel pressure
Leaking/contaminated fuel injectors
Leaking fuel pressure regulator
Low fuel pressure or running out of fuel
Vapor recovery system
* Air leaks after the MAF
* Vacuum Leaks
* Improperly seated engine oil dipstick
* Leaking gasket
* Stuck EGR valve
* Leaking diaphragm or EVR
* Oil overfill
* Cam Timing
* Cylinder compression
* Exhaust leaks before or near the HO2S(s)
Start at the top of the list and work your way down. Hope this helps.