This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
Check out some other projects from the book:
One basic tune-up procedure for just about any car on the road is the replacement of your spark plugs and spark plug wires (where applicable). I recommend replacing your spark plugs every 10,000 miles, or about once a year. In reality, you can probably go longer than that, however, you never really quite know how long the plugs are going to last, or you may forget to replace them if you don't setup a yearly schedule.
With the introduction of the Boxster 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 (spark plug wires). It's a pretty cool setup, not commonly found on older cars. 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 to 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 (Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands). Access to the plugs may be easier if you remove the fender liners in front of each wheel well, particularly on the passenger side. 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 off of - 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, it may have cracked or become contaminated: replace it with a new one (see Photo 3 and also Photo 6 of Pelican Technical Article: Camshaft Upgrade / Chain Tensioner Replacement).
Spark plug removal is easy - you just need the right spark plug wrench. I have one that I love - it's a spark plug socket with a rubber insert that catches the plug and also has a built-in swivel on the attachment end. These wrenches are readily available from the tools section of PelicanParts.com. This tool is especially useful when trying to remove plugs in hard-to-reach places.
Using a breaker bar, grip the plug and turn it counter-clockwise 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 means that the threads of the spark plug don't mesh properly with the ones in the head, instead choosing to "cut their own path." This damages the threads on the head, and in extreme cases, may destroy the threads in the cylinder head entirely. Trust me - you do not want this to happen. Proceed carefully and cautiously here.
Install each spark plug into the cylinder heads without using any anti-seize compound. Torque the spark plugs to 30 Nm (22 ft-lbs). I recently learned that Porsche, published a bulletin indicating that it doesn't recommend using anti-seize compound on spark plugs for any of their engines (Porsche Technical Bulletin 9102, Group 2 identifier 2870). 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.
Each spark plug has its own individual coil. These are attached to the engine with two bolts (purple arrows). Remove each bolt and then disconnect the coil plug harness (green arrow). The coil should be able to be pulled from the engine once loose.
This particular photo shows an individual spark plug coil (inset). The blue arrow shows the plug that powers the coil, and the orange arrow shows the mini-bellows that is part of the coil that seals the chamber and keeps dirt and debris out. Be sure that you inspect the coil packs for cracks, particularly if the car has been driven on roads covered with salt. These coil packs can corrode, crank and then cause misfires.
I like to use a swivel-socket spark plug removal tool from Craftsman. This tool is great for getting around bends and into hard-to-reach places. If you have a leaky seal on your valve cover, there is the opportunity for the spark plug holes to fill up with oil. When you pull out the spark plug connector / coil combo, you may find that it is contaminated with engine oil. If this is the case, then you should replace the spark plug tubes (yellow arrow, Boxster 1997-2004). These are plastic liners that seal the internals of the engine from the spark plug chamber. Use a pair of needle-nose pliers and simply grab the tube and pull it out of the hole. Later Boxsters and Caymans don't have tubes, but o-rings in the camshafts housings that should be inspected at this time.
In the photo inset, you can see an unusual spark plug with all four of its electrodes eaten away (red arrow). I would hazard a guess that this plug was improperly plated from the factory, and as it progressed through its life, the repeated sparking slowly ate away at the electrodes until they were gone. A plug in this condition would misfire often (if at all), and would generate poor performance for this particular cylinder. Surprisingly enough, none of the rest of the spark plugs in this set exhibited this type of damage. This is what leads me to believe it was defective from the manufacturer. On the right is shown a brand new Bosch Platinum spark plug. Spark plugs have varied over the years as engines have been changed slightly due to smog regulations. The important thing to remember is to get the proper ones for your car, otherwise you may encounter odd ignition problems (they are scaled by both electrode type and also by heat range). Spark plugs are cheap - I would go with a brand name like Bosch or NGK, and avoid the no-name brands.