So I've been having a lot of trouble with my car, specifically rough idling and turning off once in a while at stop signs/lights. At one point I had 9 error codes lol.

Changed the O2 sensor, cap and rotor, distributor, spark plugs and spark plug wires.

Now it's down to 1 error code and it says Cylinder 3 misfire.

I checked the 3 week old spark plugs and the one in Cylinder 3 was a lot more worn than the others. The gap seems fine for it so I'm not sure what's wrong?

Timing maybe?

 

When you say worn what does it look like? Is it white in colour and chalky, burnt/melted or maybe black in coulour and wet or covered in soot? Can you post a picture or maybe give a better description? Your spark plug can tell you a lot about the condition of a cylinders combustion health.

Other things to test/check;
• Distributor cap
• Distributor rotor
• Spark plug wire
• Fuel injector
• Fuel injector wire/connector
• Cylinder compression

 

It's black, not wet but maybe covered in soot.

I'll post a picture tomorrow.

Also it's a '99 Accord Ex Coupe 4-cyl

Thanks in advance!

 

Black is usually an indication of a rich fuel mixture or a week ignition/incomplete combustion.
• Perform a compression test to check the health of that cylinder. Low compression can cause a misfire.
• Check the resistance of the new plugs and wires.
• Check the fuel injector, when the car is running you should hear it clicking like the rest. If it is not clicking it could be stuck open.

New parts are not infallible. There could be something wrong with the plug or wire. Do you have a multimeter that you can run some resistance tests with?

If you can, could you post a picture of all of your spark plugs.