The brief
The A6 came in for a routine oil change, and the check that goes with it turned up a few jobs worth doing while it was on the ramp: an upper control arm and its bushing worn, the spark plugs due, and the air and cabin filters clogged. The owner had it all done in one visit, which is the efficient way. The upper control arm locates the top of the suspension and its bushing keeps the joint quiet and precise, and a worn one means a knock over bumps and looser steering. The spark plugs fire each cylinder and wear, the gap opening up, until the spark gets weak. The filters clean the air to the engine and the air in the cabin, and clogged ones choke both. None of these get better on their own, so it was the service plus a control arm, a plug set and the filters, done with genuine Audi parts.
The diagnosis
The check went through everything. On the lift the upper control arm had play in its bushing and ball joint, the cause of the knock and the vagueness; the spark plugs were worn, the gaps opened past spec; and the air and cabin filters were loaded with the dirt and dust they'd caught. The oil and a couple of fluids were due too. No other faults stored. So it was a service plus an upper control arm replacement, a full spark plug set, and the air and cabin filters: the wear items refreshed across the board.
The work
The engine oil and filter were changed and the fluids topped. On the lift the worn upper control arm with its bushing was removed and a new genuine Audi part fitted, every fastener torqued to the manual figures, then a full set of new genuine Audi spark plugs fitted, gapped and torqued, and the air and cabin filters replaced. The geometry was checked and set so the new arm sat right. A road test confirmed the knock was gone, the steering tight, the engine running smooth, and nothing leaking.
The outcome
No more knock over bumps, tight steering on a fresh control arm, smooth power on new plugs, clean air to the engine and the cabin, and the service done alongside it. The A6 went home sorted in one visit. The control arm, the plugs and the filters were exactly the things the check is for, so catching them and renewing them with genuine parts while the car was in kept them from becoming separate trips.
