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Distributor Cap and Rotor Replacement
 
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Pelican Technical Article:

Distributor Cap and Rotor Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$80 to $340

Talent:

***

Tools:

Philips head screwdriver

Applicable Models:

Porsche 993 Carrera (1995-98)
Porsche 993 Carrera 4 (1995-98)
Porsche 993 Carrera 4S (1996-98)
Porsche 993 Carrera S (1998)
Porsche 993 Targa (1996-98)
Porsche 993 Turbo (1996-97)

Parts Required:

Distributor caps, rotors

Hot Tip:

Change both caps at the same time

Performance Gain:

More power

Complementary Modification:

Change spark plugs

The 993 is a flat six cylinder engine that is the first Porsche mass produced engine to be twin plugged. This means that there are two spark plugs for every cylinder. While the motor is the first twin plugged motor it runs off of a single distributor shaft that connects to a gear on the crank shaft and then drives a second distributor rotor and cap by a belt off of the first distributor. While this article will show you how to properly change your distributor cap and rotor. Please see our article on replacing your distributor belt for additional work on your distributor.

The distributor caps and rotors will eventually wear out on your Porsche 993 as the metal contact areas take a beating during operation. Misfires can be a vacuum problem caused by cracks in both the rotor and cap, these are often very difficult to spot. If there are signs of pitting on the rotor or cap or they have over 30,000 miles on them they should be replaced. Checking them should be part of your regular maintenance.

If you own a Varioram car you will need to remove part of the blower motor assembly (red arrow) and you may need to move the A/C lines (yellow arrow) if needed.
Figure 1

If you own a Varioram car you will need to remove part of the blower motor assembly (red arrow) and you may need to move the A/C lines (yellow arrow) if needed. Please see our articles on these procedures for additional assistance.

On the non-Varioram engines you will need to remove the heat tube (red arrow) to remove the distributor caps.
Figure 2

On the non-Varioram engines you will need to remove the heat tube (red arrow) to remove the distributor caps.

Begin by carefully removing the hose attached to the nipple on the heat tube by wiggling it straight off (red arrow) and then pull off the two electrical connections (yellow arrow).
Figure 3

Begin by carefully removing the hose attached to the nipple on the heat tube by wiggling it straight off (red arrow) and then pull off the two electrical connections (yellow arrow).

Remove the electrical connection for the heater temperature sensor by squeezing in the wire on the connector and pulling it straight up and off (red arrow).
Figure 4

Remove the electrical connection for the heater temperature sensor by squeezing in the wire on the connector and pulling it straight up and off (red arrow).

Use a Philips head screwdriver or 7mm socket and loosen the two upper clamps holding the tube to the blower (red arrows).
Figure 5

Use a Philips head screwdriver or 7mm socket and loosen the two upper clamps holding the tube to the blower (red arrows).

Loosen the lower hose clamp (red arrow) and then pull the tube back and up and out from the blower assembly.
Figure 6

Loosen the lower hose clamp (red arrow) and then pull the tube back and up and out from the blower assembly.

This photo illustrates the two distributor caps with the spark plug wires attached.
Figure 7

This photo illustrates the two distributor caps with the spark plug wires attached. If you are standing at the rear of the vehicle facing forward the cylinders on the left side going forward are 1-3 and the right side are 4-6. The numbers show which wire goes where on the caps and to the proper cylinder number. If you have all of the wiring holders properly installed you will need to number and remove the wires from the distributor caps to change the caps and rotors.

There is a coil that supplies power to each cap and rotor, you can label them if you like but the coils line up with the caps (red and yellow arrows).
Figure 8

There is a coil that supplies power to each cap and rotor, you can label them if you like but the coils line up with the caps (red and yellow arrows). Remove the coil wire from the distributor caps.

There are two Philips head screws that hold each distributor cap in place (red arrows).
Figure 9

There are two Philips head screws that hold each distributor cap in place (red arrows). I find it easier to loosen the screws before labeling and removing the wires. If you have all of the wire retainers and are using them you will need to remove the wires from the caps before you can remove the caps from the distributors.

Label the wires according to the plug diagram in picture 7.
Figure 10

Label the wires according to the plug diagram in picture 7. Remember to label the upper cap differently than the lower caps wires or you can mix them up when reinstalling the wires

With all of the wires labeled you can lift the caps off.
Figure 11

With all of the wires labeled you can lift the caps off. Underneath the caps you will see the two rotors (red arrows).

The rotors are a friction fit and just pull straight up and off the shaft.
Figure 12

The rotors are a friction fit and just pull straight up and off the shaft.

Check the rotor for wear and damage.
Figure 13

Check the rotor for wear and damage. The tip of the rotor (red arrow) should look a little "charred" but not cracked or any significant signs of damage.

There is a dust cover under the rotor that helps keep out dirt and debris.
Figure 14

There is a dust cover under the rotor that helps keep out dirt and debris. If this piece is damaged or cracked you should replace it. Installation is the reverse of removal. The dust cap, cap and rotor will only fit in one direction so make sure they are seated correctly before tightening everything down.

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