Started my 97 Maxima (160K miles) today and noticed a misfire. Pulled the code, got: P0304, that is a misfire on cylinder 4. I figured it was the coil pack so i switched cylinder 4's coil pack with cylinder 2's coil pack. Erased previous code. started up, went for a drive, yet again P0304. Put the coil packs back where they were. Next, I swapped the Fuel injectors around. Still same cylinder 4 misfire, same code. Spark plugs were changed less than a year ago, I know that's not the problem. Took off the MAF and sprayed that with MAF cleaner, along with throttle body.

What else could cause a misfire on cylinder 4? I plan on taking it to Sears auto tomorrow morning. Hopefully they can diagnose what is causing the misfire. They atleast have the tools to check cylinder compression, full pressure and whatever else.

Still any help with this problem will help.

Thank You!!!

P.S. I have code P0500 and P0600 that I am not worried about. They have been on for over a year.

 

Spark plug. Don't assume anything. Check it.

 

JvG, Thank You. You just saved me a lot of money.

When I pulled the coil off, I put the socket down in there to take the spark plug out. The socket would not catch. I looked down in there with a flashlight and saw what appeared to be rubber or plastic around the spark plug base where the socket would catch. I looked at the coil pack to see if the bottom was melted, it was not. I started the car and got it good and hot, that made the black stuff pliable where i could break it up with a flathead screwdriver. Then sucked the pieces out with a straw, taped to the hose of my vacuum. Finally, I was able to get the socket around the spark plug and take it out. I then used a blade to get all the black stuff off the plug. Swapped with the plug in Cylinder 2. Took for a test drive and the misfire was fixed!

Turns out that "black stuff" was rubber. It was the rubber that is in a spark plug socket that pulls the plug out when it is loosened. When I changed my spark plugs under a year ago, I remembered looking at the socket during my spark plug installation and I noticed that little rubber piece was missing. I thought nothing of it, I though it fell on the ground or something, I was not concerned and went on to finish the spark plug install.

Well, now I know where that piece ended up... lol
I guess the rubber made it to where the coil wasn't connecting all the way around the spark plug..

Thank again JvG, I would have not checked the spark plug if it wasn't for you.

Some of the bigger pieces I pulled out:


Example of what this looks like in a spark plug:

 

They have magnetic plug sockets at autozone...just bought one last week

 

That rubber piece you found is a coil pack boot. It got stuck on the head of the sparkplug when pulling out the coil packs. I had the same problem on my auto and was able to rig up a metal hook and pull it out in one piece so I was able to reuse it. I just changed my plugs on my 97 5spd today and had no problem with the boots getting stuck. You did put a new boot on the coil pack right?

 

I will definitely invest in one of those! Thanks!

 

bumpypickle, In this case, it was not the coil pack boot. I thoroughly inspected the coil pack and it was fully intact. It was 100% the little rubber piece from my spark plug socket.

 

ah, I just assumed it was the boot lol my bad, yeah I use the magnetic socket with extension. Very convenient. I probably wouldnt have noticed that either honestly

 

Anyone else curious how he switched cylinder 4 coilpack with cylinder 1 coilpack?

 

That'd kinda explain a mis-fire, huh?

 

Woops, I meant I switched with cylinder 2!

 

The reason I said "assume nothing" is that sometimes the parts we install fail prematurely or are not istalled properly. If we assume a new part is good, we are also assuming something else must be bad. So we spend time and money replacing good older parts, or selling a car which we can't fix .

 

Couldn't have said that any better " assume nothing" always double and triple check everything!

Glad you got it fixed.