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Discussion Starter · #1 ·
I came accross this problem yesterday and started searching Google and found this forum. I took the car up to AutoZone and they pulled code P0304 - Cylinder 4 Misfire Detected. I pulled the number four spark plug out and it looks fine --- nothing abnormal looking. Can a good looking spark plug still be bad? Also, does anyone know how I can test the coil pack to see if it's bad? I have never had a distributorless vehicle before. I do have a DMM.

Oh yeah, I have a 96 Avalon.
 

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plug, wires, injector, head gasket etc are all common causes of a misfire. if you have the original wires, i think that may be your issue.
 

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Discussion Starter · #3 ·
I'm not sure if it has the original wires or not. It has a little over 200,000 miles on it and we got it from my father-in-law who did all of the scheduled maintenaces to the car --- so the wires may have been changed.

I replaced the plugs and the car runs smooth now. Does that mean the problem was the spark plugs alone? Or is there possibly something else still wrong that made the plug go bad? I don't think the injector would be bad, because that would throw off a code specific to the injector --- although, you're right that the symptoms would be the same.

One interesting thing, was that the number 4 plug had a white "X" on the top of the terminal --- it was printed and not drawn. None of the other plugs had this, nor did the new ones I bought. Maybe this was a bad plug that got put in for some reason.
 
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