Spark plug numbering needed?

100,000 MILES • 6.2L • V8 • AUTOMATIC
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VIGAN
  • MEMBER
  • 1 POST
I have to change spark number 5 because it is misfiring. Wondering which one it is.
Jan 9, 2023 at 11:23 PM
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AL514
  • ✓Experienced Mechanic
  • 5,676 POSTS
Hello, here's the cylinder layout for the vehicle. Are you getting a p0305? There is a Technical Service Bulletin on cylinder misfire codes due to carbon build up on the top of the valves. So, if a new spark plug and ignition coil don't fix the issue, you may have to look into a compression issue. Excessive carbon on top of the valves causes them to not close all the way causing a compression issue. it will be more noticeable on cold start up. With the use of Direct injection fuel systems now, most dealerships offer a valve cleaning service.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough
Jan 10, 2023 at 2:39 AM
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