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code P0304 + MAF Sensor and O2 Sensor questions

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Old Oct 27, 2015 | 07:04 PM
  #1  
floppy_disk's Avatar
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code P0304 + MAF Sensor and O2 Sensor questions

I was getting an intermittent check engine light that would turn on for a month and then turn off for a month. The error code was related to the mass airflow sensor, but shortly after I read it, it turned off and never came on again.

Now, three months later, the light came on again, but now it's P0304, which means Cylinder 4 Misfire Detected, but could be caused by a number of things. I've had the car since 170,000 and now I'm at 210,000, so I'm guessing the O2 sensors have not been replaced in +100,000 miles. Is this something I should replace either way? I've heard that it should be done this to increase fuel mileage and performance. I think I have a California car, since I bought the car from the original owner in California, but I would like to avoid spending money on replacements for all 4 of them, so should I replace all 4 of the O2 sensors, or just the two before the catalytic converter?

Also, is there a test I can do to determine that the MAF is working correctly? Any idea why it suddenly stopped causing problems? Is the MAF also something that should be replaced at regular intervals?

Finally, any advice on how to troubleshoot the P0304 code?
Old Oct 27, 2015 | 07:59 PM
  #2  
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Originally Posted by floppy_disk
I was getting an intermittent check engine light that would turn on for a month and then turn off for a month. The error code was related to the mass airflow sensor, but shortly after I read it, it turned off and never came on again.

Now, three months later, the light came on again, but now it's P0304, which means Cylinder 4 Misfire Detected, but could be caused by a number of things. I've had the car since 170,000 and now I'm at 210,000, so I'm guessing the O2 sensors have not been replaced in +100,000 miles. Is this something I should replace either way? I've heard that it should be done this to increase fuel mileage and performance. I think I have a California car, since I bought the car from the original owner in California, but I would like to avoid spending money on replacements for all 4 of them, so should I replace all 4 of the O2 sensors, or just the two before the catalytic converter?

Also, is there a test I can do to determine that the MAF is working correctly? Any idea why it suddenly stopped causing problems? Is the MAF also something that should be replaced at regular intervals?

Finally, any advice on how to troubleshoot the P0304 code?
Pretty O2 sensors have nothing to do with cylinder misfire...check the coil and the plug...and look for gas on spark plug...my injector went bad giving me a misfire... As for the MAF...resolder the wires inside the unit...and clean it...using MAF cleaner...if you don't have any codes for 02 sensors don't mess with them...swap #2 coil with the #4 coil to see if anything changes in the way the car runs
Old Oct 28, 2015 | 09:09 PM
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I checked coils, sparkplugs. The problems seems to be something else...
Old Oct 29, 2015 | 09:58 AM
  #4  
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JvG
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How did you go about checking the health of the coil and spark plugs? The most likely causes are coil, spark plug, injector. Jerrod99 s suggestions are correct. Please do not assume the problem is something else. You will go on a frustrating wild goose chase. The oxygen sensors will throw a code when they are nearly done. I replace both at the same time. Usually at the same time as an oil change. The Maf is not replaced until it fails. Re-soldering the contacts inside it is certainly worth a try.
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