P0304 misfire

Maintenance/Repairs
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1


Hello,

I have a 1999 Nissan Maxima, a few weeks ago the check engine light came on and the code is P0304, cylinder #4 misfire. How should I go about fixing this? Should I check the spark plugs and ignition coils first or is there a way to change the cylinder? Where can i get the parts for cheap?



Thanks,

Rachel

2

The misfire could be due to a faulty sparkplug or plugwire. It could also be due to other things. If the plugs haven’t been replaced for at least 40 thousand miles then a new set would be good to put in and see if that clears the trouble. If the plugwires have never been replaced then they should also be done. If the trouble still continues you may want to have a shop check things out.

3

I would first pull the #4 plug and check its condition.

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

4

Take a look at the spark plugs. If that doesn’t yield anything, pull out your oscilloscope, it’ll have the answer for you most likely.

5

Xebadaih - you just told a woman who asked if she can change out the cylinder to pull out an oscilloscope. I’m not sure she’ll follow that.

Rachel - the cylinder is part of the whole engine block - not “a part” in the engine that can be replaced. Its the big metal tube inside of the engine where the piston slides up and down to turn the crank shaft which - once connected to a transmission gets you going.

At the top of the cylinder & its piston is a spark plug, a fuel injector, and valves. The fuel injector sprays fuel in, one or two valves open to suck air in, the piston shoots up in the tube, compresses the air & fuel and then the spark plug sparks and the mixture explodes. That’s what makes it all go.

So your misfire will be because of a problem with fuel, spark or compression. Spark plugs and wires are a great place to start. If that doesn’t help, you should probably just find a mechanic that you can trust as testing things like fuel injectors, ignition coils, and compression isn’t normally something you do if you don’t work on cars a lot. Plugs & wires are pretty easy if this is a four cylinder car, and if you go to an auto parts store most folks there would be happy to explain how to do it as would folks here.

6

Thanks for all your answers. I had a good laugh when I read your post. I, as you can see, am not the most knowledgeable when it comes to cars (which is exactly why I don’t go take my car to a shop, they see me as easy money ;). My dad and I changed the ignition coils and spark plugs last year when my car first started acting up, so I think that is a good place to start. Thanks again for all of your help.

7

Rachel, if you just changed plugs last year, there’s something else going on, and it’s a pretty good bet that having a technician do a compression test on #4 will be helpful.