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Re: 2000 CIVIC System too lean Cylinder 3 and 4 misfire...
P0171: This means that the oxygen sensor has detected a lean air-fuel ratio. This can be caused due to a vaccuum leak or a problem in the HO2S circuit or the HO2S (Heated Oxygen Sensor) itself. (Bank one Sensor one). This is commonly located along the exhaust pipe. It could also be a bad Mass Air Flow sensor or a bad Engine Coolant Temperature sensor. Diagnostic checks will be needed to be carried out to be verified though
Well as for the other codes, it means #3&4 cylinders are misfiring. It is a possibility that the P0171 code mite have caused the others to show up. I can be wrong though. But it is a strong possibility. If the air fuel mixtue is too lean indeed, mis-firing will occur, unless it is an actual electronic and not a mechnical problem. By the way, when these codes appear, how is the engine's performance. Does it remain the same or behaves poorly?
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codes p 0300 through refer to misfires on each cylinder with the end number ( 301 is no 1 cylinder , 302 is no 2 cylinder ans so on)=== causes --engine mechanical fault , ---wiring---ignition/ fuel ---injector/s---ECT/ MAF sensor/s ---ECM
most misfires are from injector faults like dirty/blocked tips, low fuel pressure , no pulse or problem pulse from ECM rather than plugs and wires and coils
codes p0171 refers to system to lean bank 1===causes ---intake exhaust leak---air system---maf/vaf sensors ---fuel pressure / pump---injectors ---heated oxygen sensor ( HO2S)
code p 0172 is system to rich-====causes ---intake blocked ---EVAP cannister purge valve ---fuel pressure --EGR system---injector/s ---HO2S
couple these two codes with the misfire codes , I suggest you look at the injectors, fuel pressure (too low) from EVAP problem not venting tank, fuel pressure regulator, EGR system
P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
weak coil pack
fowling spark plugs/wires
Low fuel pressure
P0171 System too Lean (Bank 1)
P0300 Random/Multiple Cylinder Misfire Detected
check for vacuum leaks
check fuel for contamination or water
check fuel pressure
the other 2 codes could be related to these 2 codes and are manufacturer specific codes