The 4.2 FSI's cam adjuster solenoids clog their filter screens and the chain tensioner bleeds down, so variable valve timing loses authority and the top end rattles. We replace solenoids and tensioner at your home.
The 4.2 FSI V8 in the S5 and A6 adjusts its cam timing hydraulically: solenoid valves meter oil pressure to the cam adjusters, advancing and retarding the cams on command. Each solenoid has a fine mesh filter screen protecting it, and over years of heat and normal oil aging, those screens load up with debris. A starved solenoid responds slowly or not at all, the adjusters lose their authority, and the ECU logs P0011 and P0021 as the banks miss their timing targets.
The chain tensioner ages on the same oil-pressure system and fails the classic way, bleeding down, letting the chain run slack and rattle, particularly at start-up. The combination is distinctive: VVT codes on both banks, rough running as cam timing wanders, audible rattle, and often a low-oil-pressure warning flickering at hot idle as the worn hydraulic components bleed off more pressure than the system can spare.
The repair targets exactly what's failed: new cam adjuster solenoids (clogged screens aren't reliably cleanable, replacement is the proper fix), a new chain tensioner, and fresh oil of the correct spec. With pressure delivery restored, the adjusters regain their authority, the VVT codes stop returning, and the V8 idles and pulls the way a 4.2 FSI should.
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Cam Adjuster Solenoids & Chain Tensioner Replacement is a big job and shops quote $3,000–$4,500 for it. The single most valuable thing you can do before committing that is have the diagnosis confirmed independently, $100–$250 flat, at your location, no hoist needed, because a diagnosis isn't the repair. Plenty of cars arrive at that quote and turn out to need the smaller version of the problem.
And the honest scoping condition, up front: once I've seen it, I tell you straight whether it's something I can do at your place. If it needs a hoist, a press or a machine shop, I say so and point you to someone who has one. I don't take a job and figure it out in your driveway. That's the whole deal, and it's why the diagnosis comes first.
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Cam timing stuck off-target means more than codes, the engine runs with compromised combustion timing, costing power and economy daily. The sharper risk is the tensioner: a bleeding tensioner on an interference V8 is the standard prelude to chain slap, guide wear, and eventually a skip that bends valves. And if the oil-pressure light is flickering at hot idle, the hydraulic system is telling you its margins are gone. This is a fix-it-at-the-codes-stage job.
Yes, it's top-of-engine work, very much driveway territory. A day's labour, finished with a scan-tool VVT verification on both banks so you see the cam timing tracking its targets before we leave.
Multiple OEM solenoids plus the tensioner, and several hours of V8 labour at dealer rates, that's the $3,000–4,500 range. We quote one flat price for the complete job, parts and verification included, before any work starts.
They can be cleaned enough to look better, not reliably enough to trust. The screens are fine mesh, debris embeds in them, and a cleaned solenoid that re-clogs in three months wastes the entire labour bill. New solenoids are the version of this fix that doesn't come back.
Usually not, the flickering pressure light is typically the worn solenoids and tensioner bleeding off pressure, not a failing pump. We check actual oil pressure during diagnosis to be sure. If the readings point somewhere deeper, you'll hear it straight before any parts go in.
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