How to change the spark plug on your 993
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The skill level of this project is a 6 in a scale level of 1-10 (10 being the most difficult)

There are a total 12 spark plugs in a 993 engine, if you started with the left side (driver's side) and felt it was a walk in the park, you are right.  The nightmare starts on the right side.  Plan on spending at least 4 hours of your time even with the right combination of sockets, extensions and universal joints.  The rule about changing spark plugs in a tight spot is that you want to the minimal number of universal joints, what you want is to get the best direct feel of the plug when you torque it down.  Forget about using a torque wrench on this job, there are only half of the plugs you can get to with a direct extension in order for your to apply the correct torque setting with a torque wrench.  The torque setting on a torque wrench is useless when it is  used in conjunction with an universal joint.  The best way to do this is by feeling.  I was always told to turn the plug 1/4 turn after it is moderately tighten.
 

Spark Plug Information
Contributed by Chris Price

There seem to be 2 manufacturers used by Porsche: Bosch and Beru
Owners Manual states use either Type FR 6 LDC or FR 5 DTC
 
Porsche dealers supply the following:
 
** 993 Carrera and Carrera 4 **
PN# 999 170 182 90 or PN#999 170 183 90
Manufacturer: Bosch or Beru
Type FR 5 DTC (stamped on plug)
3 electrodes
Gap 0.7mm
 
** 993 Twin Turbo **
PN# 999 170 195 90
Manufacturer: Beru
Type 14F 6 LDU (stamped on plug)
2 electrodes
Gap 0.8mm
 
Now, CAUTION, the dealer first supplied me - included within a 993 maintenance kit, with the right part # for 993 Carrera, the 993 Twin Turbo 2 electrode plugs.  Not sure whether these would be OK or not - suspect not, since they had a radically different gap (ranging from .75mm to .85mm, compared to the 0.7mm per Owners Manual) and also, I think, a different heat rating.
 
So lesson is, check your part no against above - or if non-Porsche supplied aftermarket at least make sure the plugs are 3-electrode Type FR 5DTC
 
And, finally, all have told me the plugs should be pre-gapped from the factory.  Checking my 3-electrode ones, they all seem pretty close to 0.7mm spec.  However, as mentioned, the 2-electrode plugs were all over the shop gap-wise.  So worth checking - after all the plugs can be knocked about and bent in transit etc.  But I wouldn't attempt to gap the 3-electrode ones - if they were far off just return for a replacement.  Plugs are at least cheap.

Jack the rear of the car up prior to the starting of this DIY, later you will know why it is necessary to jack it up first.  For instruction on how to jack the rear of your car up please refer to the DIY section on "How to jack your car up".  After it is safly on jack stands remove your engine under tray if it is still in place.

LEFT BANK REPLACEMENT
First you will need to remove the heater ducts that are blocking your way on the left side of the motor (driver's side), please refer the the distributor cap replacement section in my DIY to find out how to remove the heater ducts. 

Remove the spark plug wires on the bottom row spark plugs by pulling and twisting the spark plug wire at the boot of the wire. (Do not pull on the wire!)  Proceed to remove the spark plug by using the spark plug socket and a long extension.  You will not need any universal joints to do the bottom side plugs.  Check the gaps on the new plug gaps before you install them, all of them should have already been pre gapped at the factory but once in a while you will get one with the wrong gap setting.  It is also a good idea to lube the threads on the new plugs with some motor oil before you install them.  Personally I use "Break free oil". 

Note: Regarding using oil to lube the threads. Per Beru's web-site, and the 993 Workshop Manual, the plug threads should never be coated with engine oil / anti-seize before fitting. (Contributed by Chris Price)  I use oil to lube the threads because I have been doing this for years and have never had a stuck plug

Proceed to remove the spark plug wires on the left top bank.  This side will require uses of spark plug socket, a 4" extension, an universal joint, and a swivel head ratchet.  Since the space on top is much tighter you will need to drop the spark plug socket and the extension in first and mount the universal joint once it is in, and then attach the ratchet.


 
 

Now you are ready for a beer break!


 
 

RIGHT BANK REPLACEMENT
Now the fun starts, first you will need to remove your air filter housing cover and disconnect the rubber snorkel that is connected to it.  And remove the right side muffler, please refer to the "Muffler exchange" procedure in my DIY to see how to remove the muffler.  On the right bank only 5 spark plugs can be removed with the right combination of universal joints and extensions.  The most inner top spark plug can only be removed by taking off the right side engine shroud.  Since you need to take the shroud and muffler off any ways, it is much easier to change all the top plugs once when you have removed all the necessary items.

Pull the top and bottom spark plug wires out first.  After the bottom plug wires are pulled from the spark plugs you want to use a flat screw driver to push the rubber seal up through the shroud opening and squeeze all three wires including the plug boot all the way up.  You will know why it is necessary to do this later.

Remove the muffler mounting bracket by unbolting one hex bolt and loosen one 13 mm bolt, below is a picture of how far you want to loosen the bolt, but you do not want to take the bolt off completely.  This will save time when you re-install the muffler mounting bracket.  Also remove the rubber hose that connects the heat exchanger to the heater ducts.

Remove the remaining hex bolt that holds the shroud on. 

Remove the 2 mounting bolt that hold the snorkel (clutch ventilation tube) to the engine case and shroud.  Only 1 bolt is showing on the picture, notice the bolt on the far left of the picture also need to be removed.

Use a needle nose pliers to open the clamp that secure the clutch ventilation tube to the transmission area.  And pull the tube off.

At this point the shroud + snorkel should drop down really easy, now you know why it would have been easier to have the spark plug wires pushed up in advance

Here is a picture of the shroud and snorkel combination.

Now look at all the extra space you have to work with to get to that inner spark plug  and the spaces you have to get others out.  You will need to remove that inner top plug from underneath the car.


 

The rest should be self explanatory......

If you want to see the condition of the spark plug after 15,000 miles click here.
 
 

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