How To Replace Spark Plugs

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  • Difficulty: Advanced
  • Avg. Time Necessary: 3-4 Hours
  • Cost: ~ $100


The spark plugs on a 993 are not too hard to change but they vary quite a bit on how easy they are to access. Standing at the rear of the car with the engine lid open, the pistons are number from 1 (left side the nearest to you) to 3 (left side, farthest away), and 4 (right side, nearest) to 6 (right side, farthest). Each cylinder has two sparkplugs, the upper and lower plug. The most difficult one is number 6 upper, primarily because you have to remove sheet metal and other parts to gain access.


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.


Tools required:

Ratchet 3/8” drive

Small ratchet 1/4" drive with 7mm and 10 mm socket

10mm spanner, 13mm spanner

Spark plug socket: Snap-on S9706KMAG (magnetic)

Wobble extension (3/8” drive) I used Snap-on FXWK4 but you can use other make

Universal joint

Extension socket 15cm and 7.5cm

6mm allen key on socket: Suggest

Duct tape

Magnetic tool (in case you drop the spark plug inside the valve cover)

Extension bar

Parts required:

BERU 14 FR-5 DTU or Bosch spark plugs FR 5 DTC X12 - They have 3 prongs and 0.7mm gap.

The lower spark plugs are relatively easy.

Remove mufflers. The clamps are a pain!

On the right lower banks, the hose from heat exchanger needs removing, the left does not (red star marks items to be removed).

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The boots of spark plugs may be a little difficult to remove but it will come out with turning and pulling. If they are stiff and would not budge you can buy spark plug pullers or carefully lever off the boots with flat-head screw driver using a cushion at the leverage point to prevent damage to the valve cover.

Label the right side leads with tape and permanent marker (I think you only need to label one on either side as if you know which labelled boot belonged to which spark plug then the middle one should go to the middle spark plug and the remaining one is easy to identify).

Remove spark plugs with socket and extension – you do not really require the wobble extension for the lower bank spark plugs.

Replace with new spark plugs (You can use a torque wrench set @ 30Nm - I suggest you get a feel of how tight this torque is as you will not be able to use a torque wrench on the upper spark plugs).

Reconnect the spark plug boots on the left bank but leave the right bank boots disconnected as you will need to push these through the opening in the engine shroud.


Left upper spark plugs


To access the upper left spark plugs, the blower assembly and the pipe work need removing.

Unscrew the 2 X 10mm hex bolt attached to the blower assembly and the 2 X 10mm bolt seen on the intake trumpet (the tube with square rubber mesh in the picture below).

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Loosen the top front jubilee clip only on the tube sitting under the intake trumpet.

Loosen the lower jubilee clip using 7mm socket and driver handle extension (this is at the base of the long pipe). Note that the pipe may be slightly different to mine.

Remove the connection marked with red stars whcih include the heating element on the tube (rectangular plastic with 2 wires attached which just pulls out).

Pull the tube out from the top end (i.e. detach from blower) and this will allow removal of the intake trumpet which cannot be removed without damage if the above procedures are not followed.

Remove the blower.

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This allows good visual and spatial access to the spark plugs.

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Unplug the spark plug leads.

Using a combination of universal joint, extension and spark plug socket (you will need to try out different combinations and tape the joints with duct tape so that the joints don’t come apart) remove the old spark plugs.

When replacing the new spark plugs, I suggest you put on some duct tape around the socket and the spark plug hex bolt so that the spark plug does not fall out as it happened to me and I had to retrieve it (once the spark plug is seated it is easy to pull the socket out even with duct tape).

Reconnect spark plug boots.

Reconnect and remount the blower assembly.

Right upper spark plugs


Top right bank spark plug change – here is where the “fun” begins.

Have a list of swear words ready!

Remove the airfilter cover (yellow star) and disconnect the rubber pipe (blue star).

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Remove the muffler bracket (see 1st image marked with red star) by unscrewing the bolt on the engine shroud and the camshaft housing (see below) – this was a pain as I rounded the bolt and I had to remove the heat exchanger to gain access. The bolt on the camshaft housing had to be cut off as you cannot fully back it out as the tensioner housing was in the way. The muffler bracket is slotted, so removal of this bolt is not required.

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Squeeze the oval rubber holding the 3 spark plug leads up into the engine shroud.

Remember that you should have labelled the leads as mentioned earlier.

Push the 3 plug boots through the opening into the shroud. Now you have a clear access to the middle bolt on the shroud.

Soak all the fasteners/bolts with WD40 or PlusGas. Unscrew all the hex bolts as shown on

When undoing the 3 Allen bolts holding the engine shroud use the long 6mm Allen key socket (see picture below) and make sure you tap it into the socket so that it is straight and not skewed (the picture below is actually during reassembly but you get the idea - the metal clutch ventilation pipe is removed here but during disassembly and reassembly you will need to remove and refit the engine shroud and the metal pipe together as you will not be able to remove or refit the metal pipe separately).

DO NOT STRIP THE BOLTS – you will wish you never started this job if you do (if you still managed to strip the bolt then pray and look at my troubleshooting section at the end).

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Disconnect the metal clutch ventilation pipe from the hose by undoing the hose clamp.

Undo the jubilee clip fastening the bent rubber hose on the clutch ventilation pipe from the engine room (you can keep this on if you want as it can be removed attached with the engine shroud). I used a very small 1/4" ratchet with 7mm socket to undo the jubilee clip.

Remove the engine shroud and the metal clutch ventilation pipe (these come off together - the pipe does not come out without removing the engine shroud).

You now have access to the spark plugs on the upper bank.

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Remove the plug boots – I levered these off by using a flat head screw driver using a “soft cushion” at the leverage point to prevent damage the valve cover.

When replacing the new spark plugs, I suggest you put on some duct tape around the socket and the spark plug hex bolt so that the spark plug does not fall out.

Refit the spark plug boots.

Thread the lower spark plug boots and wires through the engine shroud (I found it difficult to completely seat the rubber cover from below so used a long socket extension to push the rubber cover from the engine bay) and reconnect the boots to the lower spark plugs.

Refit engine shroud, the metal clutch ventilation pipe and reconnect the rubber hose to the metal clutch ventilation pipe.

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It is a little fiddly when assembling the shroud and the metal pipe together - you will need to assemble with the metal pipe passed through the hole (without the screwing it down to the shroud). Make sure you fit the shroud behind the rubber flap and you will need to slide the shroud slightly to the left (having positioned the top left corner of the shroud inside the groove of the other shroud) to pass the end of the metal clutch ventilation pipe past the suspension.

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The metal hose clamp (yellow star in above picture) requires a vice grip to fully open - pass it over the pipe made of some sort of fabric and wire rings then fit the end of the clutch ventialtion pipe into this fabric pipe and release the hose clamp. I could not keep the ring clip open wide enough with a pair of pliers.

Fasten all the bolts - I have changed these to stainless steel bolts and washers.

You are now finished! Go and have a beer




I stripped the Allen bolt as I did not use a long Allen key socket so I suggest you buy the socket shown above before you start and save yourself a load of hassle, money and time.

Once you have stripped it you have a very few options available to you. I suggest the following:

Lubricate the bolt copiously with WD40 or similar, let it soak for a while and use following methods:

Use an oversized Torx bit which you hammer into the bolt and use an extension socket to turn with ratchet (I regret not trying this method).

Use a larger hacksaw blade to cut a slot into the bolt head (try and saw so that you cut slightly below midway which may be important if everything fails) and use a large flat-head screw driver with a hexagonal socket end which allows you to use a ratchet to turn.

Failing the above you may be lucky and by using a chisel to strike the bolt in an anticlockwise direction, it may slowly break loose (I mangled the head by doing this as the bolt was seized).

If the above fails as I have, keep sawing down the slot you created (remember you were sawing slightly below midline) and cut through the bolt head and most of the washer (don’t cut through as you may cut through the shroud (this is not a major problem if you did). Using a flat-head screw driver, strike through the cut and sever the washer. Wiggle the screw driver up and down to weaken the bolt head (because you sawed below midline the bottom half should be weaker) and remove the bolt head and the washer. Try knocking out the other half of the washer with a hammer and small flathead screw driver. Lubricate the bolt copiously with WD40. Hit remaining head with chisel and hammer to rotate bolt anticlockwise. If it fails to move, lubricate, let it soak for 5 minutes and hit with chisel again. Repeat until the bolt turns.

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I tried heating with a Butane gas pencil torch, used a bolt and stud remover but didn’t work (shroud is in the way to drill deep enough and even if you did, you will not be able to use the anticlockwise drill bit as you do not have any space to attach the tap wrench on it!

If you manage to strip the bolts on either side, I think you will be able to use one of these:

Image:993 Plug Change - 013.jpg

You hammer on the appropriate sized bolt extractor and use a ratchet to turn and hopefully you will be able to remove the bolt.

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