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Pelican Technical Article:

Spark Plug Wire and Coil Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$40 to $150

Talent:

**

Tools:

5mm Allen, 10mm, 5/16th spark plug thin wall socket and extensions

Applicable Models:

VW Golf GTI (2000)
VW Golf GTI 1.8T (2002-05)
VW Golf GTI 20th Anniversary (2003)
VW Golf GTI 337 (2002)
VW Golf GTI GLS (2001)

Parts Required:

Spark plugs, coils when necessary

Hot Tip:

Work on a cold engine

Performance Gain:

Better mileage

Complementary Modification:

New air filter

Replacing the spark plugs on your GTI Mark 4 is recommended routine maintenance. Volkswagen recommends replacing the spark plugs on GTI models every 40,000 miles or five years. With all the major engine design changes over the years, spark plugs can now last up to three times as long as they did in years past. I suggest replacing your spark plugs every three years regardless of mileage. If the last time they were serviced is unknown, replace them right away. I do NOT recommend putting anti seize on the plugs.

Changing spark plugs is one of those time-honored maintenance tasks that any self-respecting car enthusiast should do themselves. It's usually easy to do and it gives you a chance to feel like a real gear head without having to get all that dirty or spend hours writhing around on the floor of your garage.

Granted, some of today's cars are packaged so tightly that it can be very difficult to reach the plugs, and some modern cars have extremely long recommended service intervals for spark plugs, further decreasing the incentive to DIY.

In the case of the 1.8T engine, however, it's quite easy to change the spark plugs. That's a good thing, because turbocharged engines tend to be harder on spark plugs, particularly when increasing the boost and/or tinkering with air-fuel ratios after performance upgrades. In addition, if your turbocharged engine isn't running quite right, it is quick and relatively inexpensive to eliminate the spark plugs as a potential source of the problem through a plug change.

The 1.8T has a coil-on-plug ignition system. All this means for the home mechanic is that the coil must be removed in order to access the spark plugs, rather than a cable running between the coil, or the distributor, and the spark plugs. Removing the coils and/or the spark plugs is necessary for some other projects, such as replacing the valve cover gasket.

One other thing you may want to consider is putting a small amount of dielectric grease on the ends of the coil pack where it attaches to the spark plug.

It is a very good idea to change the plugs when the engine is cold. If the engine is hot or warm the threads in the head a much more susceptible to damage from stripping or cross threading.

Begin by disconnecting the ground on the battery. Please see our article on battery maintenance and replacement.

The spark plugs and coils for the GTI Mark 4 are all located on the top of the engine under the engine cover. Remove the engine cover by turning the 4 plastic screws 90 degrees with a Philips head screwdriver.

With the cover out of the way you can see three of the coils; the number four coil is underneath the vacuum reservoir.

You will need to remove the vacuum reservoir to give you access to number four coil and plug. Use a 10mm socket or wrench and remove the reservoir from its mounting bracket. With the reservoir out of the way you can remove the three 5mm Allen bolts holding the bracket to the valve cover.

While you can remove the coils without removing the wiring harness it is easy to disconnect the harness from the coils and it will give you a lot more room to work. Lift back on the small tab at the top of the connection and slide the harness off the coil. Take care as the connections can become brittle over time.

Next pull the coils straight up and out of the valve cover while giving a slight twist. They will just "pop" out.

Inspect each coil for any damage.

Keep the coils in order when you remove them. If you find any thing "funky" with the plugs you want to be able to start trouble shooting with the right coil for the plug.

Use your 5/8 thin walled spark plug socket along with a long extension and remove the plugs. Note: when reinstalling the plugs it is always best to hand thread the plugs until you are sure they are properly seated.

Examine the plugs to for any issues with the motor.

Installation is the reverse of removal.

The spark plugs and coils for the SGTI Mark 4 are all located on the top of the engine under the engine cover.
Figure 1

The spark plugs and coils for the SGTI Mark 4 are all located on the top of the engine under the engine cover. Remove the engine cover by turning the 4 plastic screws (red arrows) 90 degrees with a Philips head screwdriver.

With the cover out of the way you can see three of the coils; the number four coil (red arrows) is underneath the vacuum reservoir (yellow arrow).
Figure 2

With the cover out of the way you can see three of the coils; the number four coil (red arrows) is underneath the vacuum reservoir (yellow arrow).

You will need to remove the vacuum reservoir to give you access to number four coil and plug.
Figure 3

You will need to remove the vacuum reservoir to give you access to number four coil and plug. Use a 10mm socket or wrench and remove the reservoir from its mounting bracket (reed arrow).

With the reservoir out of the way you can remove the three 5mm Allen bolts (red arrows) holding the bracket to the valve cover.
Figure 4

With the reservoir out of the way you can remove the three 5mm Allen bolts (red arrows) holding the bracket to the valve cover.

While you can remove the coils without removing the wiring harness it is easy to disconnect the harness from the coils and it will give you a lot more room to work.
Figure 5

While you can remove the coils without removing the wiring harness it is easy to disconnect the harness from the coils and it will give you a lot more room to work. Lift back on the small tab at the top of the connection (red arrow) and slide the harness off the coil (yellow arrow). Take care as the connections can become brittle over time.

Next pull the coils straight up and out of the valve cover (red arrow) while giving a slight twist.
Figure 6

Next pull the coils straight up and out of the valve cover (red arrow) while giving a slight twist. They will just "pop" out.

Inspect each coil for any damage (red arrow).
Figure 7

Inspect each coil for any damage (red arrow).

Keep the coils in order when you remove them (arrows).
Figure 8

Keep the coils in order when you remove them (arrows). If you find any thing "funky" with the plugs you want to be able to start trouble shooting with the right coil for the plug.

Use your 5/8 thin walled spark plug socket along with a long extension and remove the plugs (red arrow).
Figure 9

Use your 5/8 thin walled spark plug socket along with a long extension and remove the plugs (red arrow). Note: when reinstalling the plugs it is always best to hand thread the plugs until you are sure they are properly seated.

Examine the plugs to for any issues with the motor.
Figure 10

Examine the plugs to for any issues with the motor.

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Page last updated: Fri 12/2/2016 02:33:58 AM