Audi A4 B8: How to Replace Spark Plugs and Ignition Coils
You should change your spark plugs every 40,000 miles and your ignition coils every 80-100,000 miles. This article will show you how to change the spark plugs and ignition coils on the Audi A4 B8.
This article applies to the Audi A4 B8 (2008-2015).
Changing the spark plugs and ignition coils are an important part of maintaining your Audi A4. You should follow Audi's recommended maintenance schedule when changing spark plugs. Ignition coils can last much longer, and you won't need to change them as often, but sometimes the wires will wear out or moisture can get into coil packs. Failure of either the spark plugs or ignition coils leads to engine misfires, rough idling, and the engine running lean.
Materials Needed
- Replacement spark plugs and ignition coils
- Ratchet with extension
- 5/8" spark plug socket
- Flat head screwdriver
- T30 Torx screwdriver
- Spark plug gap tool
- Anti-seize
Whenever you're doing work on an ignition system, you should first disconnect the battery. The battery on the Audi A4 is located in the trunk underneath the spark tire.
Step 1 – Disconnect ignition coil electrical harness
Open the hood and pry off the engine cover. You'll find the ignition coils and electrical harness on the passenger's side of the engine. Start by pulling up the eight plugs on the bottom of the harness. Then remove the Torx screw holding the harness to the engine body. To disconnect the harness from the ignition coils, you'll need to push in the clips on the coil plugs. A flat head screwdriver helps when pushing in the clips.
Step 2 – Remove ignition coils and spark plugs
With the harness disconnected and moved out of the way, you simply need to pull the ignition coils out of the engine wells. You may need to wiggle them a little to get them to come loose.
At the bottom of each engine well you will see a spark plug. Attach your spark plug socket to a ratchet with an extension. Then use the socket to loosen the spark plug. Carefully pull each spark plug up and out of the engine well.
Figure 3. Spark plugs in engine wells. 
Figure 4. Spark plug removal.
Pro Tip
Be careful not to let anything fall into the engine well when the spark plugs are out, otherwise you'll have a hard time getting it back.
Step 3 – Install new ignition coils and spark plugs
Check the gaps on your new spark plugs and make sure that they match the recommended specs for your engine. If you want to make the spark plugs easier to remove, apply some anti-seize to the threads before placing them in the engine. Lower the new spark plugs into the engine well and tighten them by hand. Then tighten using the ratchet. They don't need to be too tight, but you definitely don't want them loose.
Next, insert the new ignition coils into the engine wells until they snap into place. Plug the electrical harness plugs into the ignition coils. Tighten down the Torx screw to the harness. Then reconnect the eight bottom plugs of the harness. Replace the engine cover and reconnect the battery. Test start the engine and be on the lookout for any rough idling or misfires. If it runs well, then you're all done. If not, try checking the electrical harness and the ignition coils, making sure they're connected properly.
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