How to Replace 300M Spark Plugs


A Chrysler 300M uses high performance spark plugs that efficiently deliver an electrical spark from the 300M's power distributor to the spark plugs inside the engine. The spark plugs are responsible for igniting the fuel mixture inside the combustion chamber. When this mixture is not burned efficiently, one of the common problems can be a bad spark plug. When replacing the spark plugs in a 300M, it's best to use a 4-tip platinum replacement plug due to the high performance (and high compression ratio) nature of the engine in the 300M.

Things You'll Need

  • Socket wrench
  • #25 Torx socket
  • Spark plug socket
  • Socket extension
  • Open the hood of the 300M. In the center of the engine you'll see the "3.5L 300M" logo. On the left and right side of the engine, you will see a bank of wires and plugs. These are the spark plugs. They're held in place by a #25 Torx screw-bolt.

  • Loosen the coil assembly screw-bolt with the #25 Torx socket and socket wrench. These screws are on pretty tight.

  • Pull the plug end out of the engine.

  • Attach the socket extension and spark plug socket onto the socket wrench and lower the socket over the spark plug.

  • Make sure the socket has a firm grip on the end of the spark plug and turn the plug counterclockwise to remove it.

  • Pull the spark plug up and out of the engine with the spark plug socket.

  • Pull the old spark plug out of the spark plug socket and insert the new plug into the socket with the electrodes (the prongs) facing out of the socket.

  • Lower the plug into the engine's plug well.

  • Thread the spark plug. You need to be extremely careful. These spark plugs will easily cross thread, which will make it impossible to fully tighten the spark plug. So, when you first start, do not force the plug. It should thread very easily. Once you have the first few threads started, go ahead and tighten the spark plug. The rest of the installation is the reverse of removal.

Related Searches


  • "Chrysler LHS, Concorde, 300M, Dodge Intrepid Repair Manual 1998-2004"; Eric Godfrey, John H. Haynes; 2008
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