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I have a 2006 Cadillac STS. I believe the engine is a 4.6 because under the hood it says V8 but correct me if I’m wrong. I took my car to autozone to get the check engine light read and it showed different engine misfires and also the code P0300. I thought that it was possibly the fuel injectors since that’s what the man at autozone recommend me to change. When I start my car it starts shaking automatically. Whenever I can driving it hesitates and doesn’t have as much get up and go whenever I step on the gas. The engine light also blinks constantly at me. Yesterday I was looking under the hood and I seen my fuel injectors and they looked brand new. A mechanic over the phone told me that it was most likely my spark plugs and to start there and if the code did not go away that it could be a coil. I am wondering where the spark plugs are located on my car. I’m planning on changing them myself. I have tried to google and look at YouTube videos but there is not one for my specific car. Does anyone know where the spark plugs are located on my vehicle?

Answers from the Automotive Experts

Jessica Howe, Automotive Expert & Coach at


For diagrams like these, and step by step procedures, the best option is to purchase or download a repair manual for the vehicle. These manuals cover the ignition systems and much more. There are several options available online and in automotive parts stores. Keep in mind, your model will be very similar to and share a manual with other GM models and years. 

Your plugs are a little harder to get to than some. When locating the spark plugs, look for the wires leading to the coils. If you can not tell the difference between the spark plugs and other sensors on the engine, look for the 8 sets of wires which look exactly the same that run along both sides of the engine. These wires will be visible best after removal of the plastic engine covers, and the air intake. Once you have located all 8 plugs, you will have to remove the coil on top of each plug before you can get to them. You can then use a spark plug socket with an extension to reach down and remove the spark plug. 

Once you have access to the spark plugs, replacing them is easy. Good luck!

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