The brief
This A4 was in for its scheduled service interval, with no fault to chase. But the owner had read the maintenance schedule and wanted two extra jobs done while the bay was open: the spark plugs, which were past 60,000 km, and the ignition coils, which were past 120,000 km.
That is the smart way to handle this kind of work. The plugs and coils both sit at the top of the engine, and getting at them is most of the labour. Doing them together, during a service the car was coming in for anyway, means paying that access labour once instead of three times.
An owner who plans maintenance around the schedule rather than around the next breakdown ends up spending less over the life of the car. This was that kind of visit.
The diagnosis
Diagnostic scan first. No stored fault codes anywhere, which is the result you want going into a planned service.
We pulled the spark plugs for a look. The electrode wear was about what you would expect for the mileage: rounded off, gap opened up a touch, due for replacement but not catastrophic.
The coils got bench-tested individually. Two of the four measured high secondary resistance, consistent with their age and the mileage. The other two were still healthy, but on the same age clock, so doing the full set made sense rather than leaving two ageing units in place.
The rest of the consumables, filters, fluids, battery, were within tolerance. We noted the air filter is getting close to due, so the owner knows it is on the horizon for next time.
The work
Started with the service items proper. Engine oil drained warm, refilled with the correct VAG spec to volume, new oil filter fitted.
Then the plugs. All four out, all four replaced with new VAG-spec units gapped to the workshop manual figure and torqued in carefully. Plugs do not forgive being over-tightened, so each one gets the manufacturer's torque, no more.
Then the coils. All four replaced with new VAG-spec units, harness clips reseated properly on each one.
Fluid levels checked and topped where needed. Brake pads and discs inspected. Tyre pressures set, lug torque confirmed, service interval indicator reset on the scan tool.
A road test through a full drive cycle confirmed the ignition work, with the misfire counters reading zero across every cylinder.
The outcome
Idle smoothed out, no fault codes after a full drive cycle, the engine running clean.
The A4 went home with the service log signed off and the next interval noted, and with the ignition system reset for another long stretch rather than picking off plugs and coils one at a time over the coming years.
For the owner, this is what planned maintenance looks like done right: the consumables refreshed, the known wear items handled while the access was already open, and a clear picture of what is coming next. The kind of paper trail and condition that also holds the car's value when it eventually gets traded in.