# errors P0171 and P0304



## fradon (Jul 9, 2005)

Help, keep getting the P0304 code (cyl 4 misfire). Already changed the plugs and wires. Also looked for any bad vacuum leaks but may have missed it. After doing the above and resetting the code it came back in a month along with another code P0171.


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## Asleep (Jan 19, 2003)

fradon said:



> Help, keep getting the P0304 code (cyl 4 misfire). Already changed the plugs and wires. Also looked for any bad vacuum leaks but may have missed it. After doing the above and resetting the code it came back in a month along with another code P0171.


im assuming you have a 2nd gen since you posted in this section...
this is what i came up with when i checked the codes
*P0171* Fuel Injection System Lean 
when was the last time the o2 sensor was changed?


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## fradon (Jul 9, 2005)

AsleepAltima said:


> im assuming you have a 2nd gen since you posted in this section...
> this is what i came up with when i checked the codes
> *P0171* Fuel Injection System Lean
> when was the last time the o2 sensor was changed?


Never! There is only 43k on the car and its a 2000. How about the cyl 4 misfire. What is a 2nd Gen?


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## Asleep (Jan 19, 2003)

fradon said:


> Never! There is only 43k on the car and its a 2000. How about the cyl 4 misfire. What is a 2nd Gen?


a 2nd gen is an altima from 98-01. first gens would be from 93-97.5. the cylinder misfire could be from the spark plug not firing or even the injector not spraying. an injector not spraying could cause a lean condition. "lean" is more air than fuel in the combustion process. the interval on the o2 sensor is 65k miles or so... you would think it would still be good with only 43k miles... it could still be bad though. whats your gas mileage like? normal or down from normal?


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## fradon (Jul 9, 2005)

AsleepAltima said:


> a 2nd gen is an altima from 98-01. first gens would be from 93-97.5. the cylinder misfire could be from the spark plug not firing or even the injector not spraying. an injector not spraying could cause a lean condition. "lean" is more air than fuel in the combustion process. the interval on the o2 sensor is 65k miles or so... you would think it would still be good with only 43k miles... it could still be bad though. whats your gas mileage like? normal or down from normal?


Yeh only 43k, bought it from my father in-law. Like I mentioned I already changed the plugs, wires , dist cap and rotor so I guess I need to look into the injector. Do you think having a fuel injection cleaning will do the trick or will it be more complicated? Also where is the o2 sensor? I know its on the exhaust manafold but where, near the engine or under the car?


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## KA24Tech (Feb 2, 2004)

It could be an intake vacuum leak around cyl.4. Check all the hoses. To check the injector put a large screwdriver on the injector while it is running and place your ear on the large end. Listen to all of them to compare the sound.

Troy


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