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Audi A4 Coil and Spark Plug Replacement
 
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Pelican Technical Article:

Audi A4 Coil and Spark Plug Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$20 to $250

Talent:

**

Tools:

5/16th-inch spark plug thin wall socket and extensions, Philips head screwdriver

Applicable Models:

Audi A4 1.8 T (2002-08)

Parts Required:

Spark plugs, coils

Hot Tip:

Work on a cold engine

Performance Gain:

Better mileage

Complementary Modification:

New air filter

Replacing the spark plugs on your Audi A4 is recommended routine maintenance. Audi recommends replacing the spark plugs on A4 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. 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. Dielectric grease helps to keep the rubber boots from drying up and cracking. When the rubber boots crack, they can leak voltage out.

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 are 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 A4 are all located on the top of the engine under the engine cover.
Figure 1

The spark plugs and coils for the A4 are all located on the top of the engine under the engine cover. Remove the engine cover by turning the 3 plastic screws (red arrows) 90 degrees with a Philips head screwdriver.

With the plate out of the way you can see the coils (red arrows).
Figure 2

With the plate out of the way you can see the coils (red arrows).

Remove the wiring harness from the coils.
Figure 3

Remove the wiring harness from the coils. 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 4

Next, pull the coils straight up and out of the valve cover (red arrow) while giving a slight twist. They will just "pop" out. They make a special tool to pull the coils but just take your time and they will come right out. Do not wedge a screwdriver or pry bar under them as it will break off the plastic ridge along the bottom of the coil.

Inspect each coil for any damage (red arrow).
Figure 5

Inspect each coil for any damage (red arrow).

Number the coils when you remove them.
Figure 6

Number the coils when you remove them. If you find anything "funky" with the plugs you want to be able to start trouble shooting with the right coil for the corresponding plug.

Use your 5/8th-inch thin walled spark plug socket along with a long extension and remove the plugs.
Figure 7

Use your 5/8th-inch thin walled spark plug socket along with a long extension and remove the plugs.

Examine the plugs for any issues with the motor.
Figure 8

Examine the plugs for any issues with the motor. Note: when reinstalling the plugs it is always best to hand thread the plugs until you are sure they are properly seated. Installation is the reverse of removal.













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