Just started getting a restricted performance message with check engine light. Code shows P0308 - #8 cylinder misfire. Car has been running a little rough at idle when started cold (and outside temps around 40F), runs a little rough at speed for about 30 minutes then runs smooth. If the restricted performance doesn't come on within 30 minutes, all is well.
Any thoughts or votes for:
Spark plug or coil?
I do not know history of when either were last changed.

Always something, I bought the car not running, got it running, then replaced a lot of suspension parts and brakes and now it doesn't like when I drive it all over.

 

Process of elimination. Switch coil on B4 cylinder with any other one and see if the code changes from P0308. For example, if you switch B4 with B1 and the coil is faulty, you should then get code P0305 instead.

Whilst doing the swap, check the plug for gap and spark.

Graham

 

Last night I removed the #8 coil and spark plug. The plug tip was very dirty and likely fouled. Conveniently, the #8 sits under the coolant reservoir and oil fill cap and would be the first location in which any excess spilled fluids would go. I had purchased a new spark plug and installed it along with swapping the #8 coil with the driver side front coil. I cleaned all parts and reinstalled. 100 miles of driving and no issues, check eng, or restricted performance. I'm hoping the $5 spark plug did the trick. Thanks for the tip. I wish all repairs were this simple.