Pelican Technical Article: Replacing Spark Plugs and Coils Wayne R. Dempsey
Time: 2 hour
Tab: $20
Talent:
Tools:
Spark plug wrench
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
Spark Plugs, spark plug tubes
Hot Tip:
Don't use anti-seize on the plugs when installing
Performance Gain:
Cleaner, better running engine
Complementary Modification:
Replace spark plug tubes
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 sample 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.
Figure 1
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.
Note: For model year 2003 and newer, the plastic spark plug tubes were replaced with the metal tubes that only get serviced during engine disassembly.
From the 2003 Boxster Service Information Book - under engine changes:
"The oil protection tubes are now a component part of the valve lifter housing and sealed to the cylinder head cover with formed oil seal rings."
March 29, 2012
jska
Comments: How in the heck did you get a torque wrench in those type spaces? I could only manage it on the middle plugs on both sides. I ended up just tightening the plugs good and tight. Hope I didn't torque to much or too little.
February 28, 2012
boxdogg
Comments: Is there a recommended replacement timeframe for the sparkplug coil packs? My coil packs appear to be fine still at 50K miles. . .thanks.
February 3, 2012
SGHokie
Comments: I couldn't get the needle nose pliers to pull out the tubes. I found at home depot a piece of 3/4 threaded pipe fit perfectly in the hole and I was able to get the tubes out very easily. At the home depot they have small pieces that are threaded on both sides. I used a 2" piece, 1.5", and a tee. Depending on the clearance around the tube, you might want to screw the tube in first and then put the tee on. Or you can get a cap to put on the end of the tube and then use a screw driver to pry it out.
January 21, 2012
bdub
Comments: I followed the proceedure and when I started the engine after completing the work, the motor sounded a bit rough and the check engine light came on. What did I screw up or need to check?
January 3, 2012
Hurdigurdiman
Comments: Wayne..Is this the same procedure for the C2 996 3.4ltr engine? Is the 996 engine referred to as the Boxster engine? If its the same procedure I will be changing my plugs very soon as I have no idea when they were last done.
November 28, 2011
Followup from the Pelican Staff: Yes. With the exception of a few slightly different exhaust components in the way, the procedure is almost identical for the 996 Carrera engine. We will be having a 996-dedicated article on this, coming out soon. - Wayne at Pelican Parts
kimberboy
Comments: One of the coils on my '02 Boxster S has some oil seepage. Is the "tube" you mention in this artcle the problem? If so, what's the part and is it replaced while doing the plugs. My mechanic thought it was something with the coil and quoted a price of $6-700 to replace, but it seemed strange that there would be oil there.
Comments: Trying to pull out the tube with a set of needle nose inserted and opened up, I cracked/broke the tube. Does the broken pieces of plastic in there pose any danger?
Follow-up: The broken piece seems to be a perfect fit into the tube. So *if* any bits of plastic made it's way into the camshaft area, they're very very small.
Thanks Pelican for supplying all the parts I used this weekend to do my 60K service! Your technical articles and 101 Projects book really made it fairly easy to accomplish.
August 28, 2011
Followup from the Pelican Staff: I would indeed try to get all of the plastic bits out of there, as they can clog oil passages if they get stuck in the wrong places. But, generally, I would say that the likelihood of that would be pretty low. - Wayne at Pelican Parts
Canongate
Comments: I purchased new plugs for my 2005 boxster from you. They have 4 prongs electrodes?. Do I gap these or are they pre set. If I gap them what is it?...thanks
July 14, 2011
Followup from the Pelican Staff: In the old days, it wasn't uncommon to find plugs that were new with the wrong gap. However, in the past decade, I have yet to find a plug that is not correctly set from the factory. So, I've gotten a bit lazy, and I don't typically check, unless it's for a race motor or something like that. As for the plug gap, I don't have this information handy, I think it might be in the Bentley manual, although I can't remember seeing it there. In general, the four-pronged plugs can't really easily have their gap reset either. - Wayne at Pelican Parts
Roger Lenkin
Comments: What is the torque used to tighten the coil pack bolts on a 06 Boxster? Your book, 101 projects is great! Thanks ,
April 23, 2011
Followup from the Pelican Staff: Hi Roger, the factory documentation shows that these bolts are sized M6, and should be tightened to a value of 10 Nm (7.5 ft-lbs), which is not a heck of a whole lot. Be careful not to overtighten them, or the bolt / screw might snap off. - Wayne at Pelican Parts
leapin
Comments: question on plug gapping.Is the gap measured on each electrode
May 28, 2010
Followup from the Pelican Staff: Yes, the gaps are measured on each electrode. - Wayne at Pelican Parts
Check out some other sample projects from the book:
