2006 Audi RS4 4.2L Petrol · KF06 FOC

A pattern of front-end suspension wear, recurring brake disc surface degradation, and exhaust sensor irregularities dominates the mechanical record of this 2006 Audi RS4, painting a picture of a performance-oriented vehicle showing the typical wear points of its age and configuration rather than a chronic structural failure issue. The most recent test on 8 May 2026 returned a clean pass with no advisories, and the prior test on 8 May 2025 was likewise defect-free, suggesting that the underlying issues flagged in 2023 and 2024 were addressed. However, the 2024 testing cycle was particularly difficult: three separate failures were recorded within roughly two months, all centred on the exhaust lambda reading falling outside specified limits after the second fast idle, a major category defect under the emissions section. That same 2024 cluster also produced fracture advisories for both rear coil springs, a structural safety item, alongside a noted play in both front track rod arms. While these were resolved to achieve a pass on 25 April 2024, the timing and density of those failures warrant attention, as three failed attempts within a short window is an unusual concentration. Mileage stands at 124,269 miles over a twenty-year recorded life, equating to an annual accumulation of approximately 6,213 miles, broadly in line with the typical usage profile for a car of this vintage. There are no significant gaps in the annual testing record that would suggest extended periods off the road, and the mileage appears to have accrued steadily given the continuous year-on-year MOT entries. For a high-performance saloon of this era, this level of use means that suspension consumables, brake components, exhaust hardware, and engine ancillaries have all been worked regularly, which can be broadly neutral: parts have been exercised rather than left to deteriorate through standing, but consumables will have required replacement at standard intervals. The combination of moderate annual mileage and concentrated 2024 advisories points to parts reaching the natural end of their service life rather than to neglect or abuse. For a targeted inspection, priority should be given to the front suspension geometry, specifically the track rod arms and the curved control arms whose perished ball joint dust covers were flagged in 2023. On a test drive, listen for clonks or knocks from the front end over speed humps and uneven surfaces, and feel for any vagueness, wandering, or inconsistency in the steering, particularly under braking or during rapid direction changes. Examine the rear coil spring seats for any visible sagging or uneven ride height, as fractured rear springs can recur and a slight reduction in ride quality may indicate one beginning to fail. The brake discs, which were flagged as pitted or scored across all four corners in 2022 and again on the rears in 2023, should be inspected for lipping, runout, and hot judder under sustained braking, paying particular attention to pedal feedback and any vibration through the steering wheel. Finally, the repeated exhaust lambda failures in 2024 warrant a focused check of the oxygen sensors, catalytic converter efficiency, and any exhaust leaks upstream of the lambda probe, as a persistent out-of-range reading can indicate a sensor that has drifted or a pre-cat leak drawing in atmospheric oxygen. Have the vehicle run from cold and watch for any exhaust smoke or unusual ticking, and verify that no warning lights are present on the instrument cluster. The nearside rear tyre has carried a recurring nail advisory across multiple years, suggesting either persistent road hazard exposure or limited tyre rotation, so confirm that the sidewall is sound and that the current tyres have adequate remaining tread. A compression test and a borescope inspection of the cylinder bores would be prudent given the vehicle's age and mileage, as these are not visible from MOT data alone but are relevant to any high-performance V8 of this vintage.