# MY Experience with the Dreaded P0304 code - Cylinder 4 misfires.



## vincy24 (Sep 22, 2011)

I purchased a 91K 02 Nissan Altima 2.5SL 4 months back. 
The car has been running fine for the last few months returning me a decent 23mpg with Moderate to heavy rush hour traffic drive to work. 

Last Thursday the car started stuttering a bit at lights in idle. Whoever while driving I didn’t feel anything.
ON Friday morning the car started effortlessly but with a terrible idle vibration. Half mile into driving to work, the Service Engine Soon light started Flashing. 
I knew a flashing SES light means something really bad. The steady SES light means emission related and not something that will stall the car and leave me stranded somewhere Midway.
I ran a Code scan at AutoZone which returned a P0304 code - Cylinder 4 misfire.

I read on this forum that the P0304 code can be attributed to 
1) Bad spark plugs 
2) Bad Ignition Coils
3) Air Intake Leakage
4) Cylinder vacuum leaks.
5) Head Gasket leaks.

The first 2 being minor and can be easily fixed and next 3 requiring significant work
Car was garaged for 2 days and I dropped it my nearest Meineke at Winchester, MA. The Mech said this is a common problem and he will replace all 4 spark plugs $14.99 each and 1 ignition coil $84.xx 
Labors and shop supplies roughly $110 totaling to 260$
The new spark plugs and ignition coil fixed the issue for me and the car pulls much stronger now from standstill and rolling acceleration is better. I guess the combustion is now slightly better with the new plugs. 

I was lucky to be spared without significant expenses.

The mech was very helpful and honest in telling me that the changes he did can be easily done by me.

His Simple instructions were as below
Remove 4 screws to open the plastic Engine Cover
Remove a single screw from the ignition coil over the cylinder that is misfiring.
Remove the wire connector from the coil.
Pull out the Ignition coil.
Replace the Spark plug (if old, not req in my case for 20 30 k miles.)
Replace the ignition coil with a new one.
Replace the screw for the ignition coil.
Replace the 4 screw of the Engine Cover.
Clear Error code by your scanner and enjoy the drive. 

The ignition coil is available over the counter at AutoZone for roughly $74

The Mech at Meineke was very helpful and honest. He has made me a repeat customer


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## Bigstauf (Dec 12, 2011)

Facing engine left is #1 through #4 on the drivers side? I have a misfire on #4 also and will swap the coil to see if the problem moves with the coil/wire. Can anyone verify on the 02 Altima 2.5 if I am correct on the cylinder layout?


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## smj999smj (Jan 1, 2006)

#1 cylinder is at the front of the engine and closest to the side of the engine with the belts, alternator, AC compressor, etc. Cylinder #4 is at the rear of the engine, or the side of the engine closes to the transmission.


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