Autopapyrus · Audi A4 1.8 ADR (1997)
https://autopapyrus.com/guides/audi/a4/spark-plug-replacement/
https://autopapyrus.com/guides/audi/a4/spark-plug-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.
Audi A4 1.8 ADR (1997): Spark Plug Replacement
The ADR is a 4-cylinder, 20-valve gasoline engine. The spark plugs sit in wells in the cylinder head under the ignition coils. The job is not difficult, but the plugs are deep in the wells, so the main thing is to keep dirt from falling into the well and to avoid overtightening a plug in the aluminum head.
Part
| № | Part | Alternatives |
|---|---|---|
| 01 | Spark plugs, triple- or multi-electrode, same thread reach and heat range as original4 pcs | NGK, Bosch, Champion, Brisk |
Tools
7- 16 mm spark plug socket (with rubber insert) and extension
- ratchet
- torque wrench
- flat-blade screwdriver
- hex key or socket for the coil mounting bolts (as applicable)
- copper grease for coil boots
- compressed air or a small brush
There's a full repair manual for this car
Every system, wiring diagrams and torque specs — not just this job. Haynes and 17 more.
See manuals →
Step by step
13 steps- Work on a cold engine (an aluminum head can easily lose its threads when hot). Turn off the engine and remove the key. If you wish, disconnect the negative battery terminal.
- Remove the decorative plastic engine cover. It is held by clips or rubber mounts and can be pried off with a screwdriver.
- Check how the ignition is connected. On the ADR, each plug is covered by its own coil or boot. If you have high-voltage wires instead of coils, label cylinders 1-4 before removal so you don't mix up the order.
- Press the locking tab on each coil's connector and pull off the plug. Pull only on the plastic housing of the connector, not on the wire.
- Remove the coil mounting hardware (hex key or socket, size depends on the version). Pull each coil straight up out of the well, rocking it gently along its axis. If you have wires instead of coils, grip them by the boot, not by the insulation.
- Blow out the wells with compressed air, or clean them with a brush and a vacuum. No dirt should fall into the cylinder when you remove the plug.
- Remove the plugs with the 16 mm socket and extension. Apply force smoothly and keep the wrench exactly in line with the well so you don't crack the insulator. Do one plug at a time and compare it with the new one right away.
- Evaluate the condition of the removed plugs: carbon deposits, oil, or heavy electrode wear indicate the condition of the engine. A plug wet with oil points to a leak from under the valve cover or a problem with the valve stem seals.
- Check the gap of the new plugs with a feeler gauge. For the ADR it is usually 0.8-1.0 mm. The exact value is on the plug packaging or in the manufacturer's table. Multi-electrode plugs often must not be bent, since the gap is set at the factory and should not be adjusted.
- Apply a thin layer of copper grease to the threads only if the plug manufacturer allows it (on most plugs the threads are already treated and grease is not needed). Start threading the plug in by hand, or with a rubber hose on the end of the plug, so you don't cross-thread it.
- Tighten the plugs with a torque wrench. As a guide, use 25-30 N·m (18-22 lb-ft) for M14x1.25 in an aluminum head (check against the plug manufacturer's recommendation). Do not overtighten.
- Put a drop of grease on the inside of the coil boot. Seat the coils or wires until they click, snug the coil mounting bolts lightly (about 5-10 N·m (4-7 lb-ft), no more), and connect the connectors.
- Install the engine cover and reconnect the battery terminal. Start the engine and make sure it runs smoothly, without misfiring, and that no error indicator appears on the dash. If you disconnected the battery, reset the clock and radio.
Common mistakes and warnings
- Do not touch the coils or wires while the engine is running, as the voltage is high
- Replace the plugs as a set, all of the same brand and type
- If a plug is badly seized, run the engine briefly before removing it, then shut it off, let it cool to warm, and treat the plug with penetrating oil
- Do not lean over the hot exhaust manifold
- Follow the replacement interval specified for your plugs (about 30,000 km (18,000 miles) for ordinary nickel plugs; for long-life plugs, follow the manufacturer's instructions)