Replacing Your 911 Carrera (or Boxster/Cayman) Spark Plugs

The replacement of your spark plugs and spark plug wires, or coil packs, is a basic tune-up procedure. I recommend replacing your spark plugs every 10,000 miles. In reality, you can probably go longer than that; however, you never really quite know how long the plugs are going to last.

With the introduction of the Boxster / Carrera engine, Porsche eliminated the use of spark plug wires by integrating six small spark plug coils that sit on top of each spark plug. While this configuration may be a bit more expensive than the typical single coil, single capacitive discharge box configuration, it makes the car’s ignition system more reliable by removing a component that constantly wears out and fails. As manufacturing components have become increasingly inexpensive, ignition setups like these have become more common.

Begin by prepping the car. The only thing that you really need to do is make sure that the car is cold. If you try to remove or install spark plugs in a hot car, then you may encounter problems with the spark plugs gumming up or damaging the relatively delicate threads in the aluminum cylinder head. Make sure that the car is cold or, at the bare minimum, only slightly warm to the touch.

Jack up the car. While you do not need to remove the wheels to change your plugs it will give you a little more room to move if you do. There are shields protecting the heads that will need to be removed on both sides of the engine before you can get access to the coils. On the 996 Carreras each cover is held on place by 2 10mm bolts, on the 997s they have changed to 8mm Torxs. Simply remove them and place them aside.

For each coil, remove the two bolts that attach it to the engine. Unplug the coil wire harness. Then simply remove the coil/plug assembly and place it off to the side. All of the coils are the same, so it doesn’t matter which cylinder bank it came from, unless you are specifically trying to troubleshoot a bad coil fault code that was displayed by the main computer.

With the coil assembly removed, you should be able to look down the hole and see the spark plug hiding in there. If the tube has oil in it, the bellows may have cracked or become contaminated. You should replace it with a new one.

Spark plug removal is easy; you just need the right spark plug wrench. I have one that is a spark plug socket with a rubber insert that catches the plug and also has a built-in swivel on the attachment end and is available at www.pelicanparts.com

Using a breaker bar, grip the plug and turn it counterclockwise until it is loose. Then pull out your tool and grab the plug. When the plug comes out, you may want to take a close look at it. The spark plug is really the best way to visually “see” what is going on inside your combustion chamber.

Install your new plugs using a torque wrench to measure the amount of torque applied to the plug. This is very important, as it is easy to over- or under-tighten spark plugs. Make sure that the plug is firmly seated in your spark plug socket, as it is very easy to insert the plug into the head and have it cross-thread. This damages the threads on the head, and in extreme cases, may destroy the threads in the cylinder head entirely. Proceed carefully and cautiously.

Install each spark plug into the cylinder heads without using any anti-seize compound. Torque the spark plugs to 30 Nm (22 ft-lbs). Porsche published a bulletin indicating that it doesn’t recommend using anti-seize compound on spark plugs for any of their engines. The bulletin applies retroactively to all models, and the theory is that the anti-seize tends to act as an electrical insulator between the plug and the cylinder head. This could have detrimental effect on the firing of the spark due to the loss of a good, consistent ground connection.

With the new plugs installed and tightened to the correct torque, you can replace the coils and reattach the coil connectors. When you’re done, your engine should look back to normal and run perfectly.

Reprinted from www.pelicanparts.com
Full article: http://www.pelicanparts.com/techarticles/Boxster_Tech/07-ENGINE-Plugs_-_...

 

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