The B7 S4 with its 4.2L V8 is a thrilling driver's car undermined by catastrophic engine failure risk from timing chain guides and a harsh DSG transmission that eats mechatronic units. Budget heavily for deferred maintenance or walk away.
Timing Chain Guide and Tensioner Failure Leading to Engine Destruction
Common · high severity
Typical onset: 60,000-120,000 mi
Symptoms: Cold-start rattle for 2-3 seconds that worsens over time, Metallic rattling from front of engine at idle, Check engine light with cam correlation codes, Catastrophic failure: sudden loss of power, severe grinding, seized engine
Fix: Engine-out job required. Replace all timing chains, guides, tensioners, and variable valve timing actuators. Minimum 25-30 hours labor. If guides have failed and metal contaminated the engine, full rebuild or replacement required adding another 40+ hours.
Estimated cost: $6,000-9,000 preventive / $12,000-18,000+ after failure with engine damage
DSG Mechatronic Unit Failure
Common · high severity
Typical onset: 70,000-110,000 mi
Symptoms: Harsh or delayed shifts, especially 2nd to 3rd gear, Transmission slipping or jerking during acceleration, Fault codes for clutch adaptation or mechatronic communication, Transmission goes into limp mode or won't engage gears
Fix: Replace or rebuild mechatronic unit (valve body with embedded computer). Transmission removal not always required but recommended for thorough inspection. 8-12 hours labor. Software adaptation required after replacement.
Estimated cost: $3,500-5,500
Carbon Buildup on Intake Valves
Common · medium severity
Typical onset: 50,000-80,000 mi and every 50k thereafter
Symptoms: Rough idle and misfires at cold start, Loss of power and sluggish throttle response, Increased fuel consumption, Check engine light with multiple misfire codes
Fix: Direct injection with no fuel wash on valves causes inevitable carbon deposits. Walnut blasting required—media blasting intake ports with engine partially disassembled. 6-8 hours labor. Not a one-time fix; needs repeating.
Estimated cost: $800-1,200
Transmission Oil Cooler and Thermostat Failure
Common · medium severity
Typical onset: 80,000-130,000 mi
Symptoms: Transmission temperature warning light, Harsh shifting when cold that improves when warm, Coolant or transmission fluid mixing causing milky fluid, Overheating transmission leading to limp mode
Fix: Replace transmission oil cooler, thermostat, and flush both cooling system and transmission. Often discovered during routine fluid service. 4-6 hours labor.
Estimated cost: $1,200-1,800
Control Arm Bushings and Ball Joints
Common · medium severity
Typical onset: 70,000-100,000 mi
Symptoms: Clunking over bumps from front suspension, Wandering or imprecise steering, Uneven tire wear, especially inside edges, Vibration through steering wheel at highway speeds
Fix: Multiple control arms per side with pressed-in bushings that fail. Audi doesn't sell bushings separately on most arms—require complete arm assemblies. Front suspension overhaul typically means 6-8 arms plus ball joints. 8-10 hours labor plus alignment.
Estimated cost: $2,000-3,500
Fuel Pump Controller (HPFP Driver) Module Failure
Occasional · high severity
Symptoms: Random stalling or no-start condition, Rough running and hesitation under load, Fuel pump relay clicking repeatedly, Check engine light with fuel pressure/volume codes
Fix: Replace fuel pump control module mounted under rear seat. Common failure point causes pump to run erratically or not at all. 2-3 hours labor including diagnosis.
Estimated cost: $600-900
Rear Differential Mount and Transmission Mounts
Occasional · low severity
Typical onset: 80,000-120,000 mi
Symptoms: Clunking from drivetrain on throttle transitions, Vibration felt through floorboard during acceleration, Excessive driveline movement visible during hard launches
Fix: Rubber mounts deteriorate from heat and torque. Rear diff mount is subframe-out job (8-10 hours), transmission mounts easier at 3-4 hours. Often done together during major service.
Estimated cost: $1,200-2,200 for all mounts
Owner tips
Replace timing components BEFORE 80k miles even without symptoms—this is survival maintenance, not optional
DSG fluid changes every 35-40k miles with OE-spec fluid can extend mechatronic life
Walnut blast valves every 50k miles; Italian tune-ups don't prevent buildup on direct injection
Buy only with complete service records showing timing work already done or budget $8k immediately
Pre-purchase inspection must include borescope of cylinder walls and timing chain inspection
Only for enthusiasts with deep pockets or DIY skills—phenomenal chassis and powertrain dynamics, but ownership cost rivals exotic cars due to engine time-bomb and transmission fragility.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: AGM battery required; located in trunk under floor panel; high power demands from V8 engine and AWD system
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Every control module on the 2004-2007 Audi S4 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
📍 Integrated into ABS module or separate module in trunk
🔧 VCDS
⚠️ Optional; indirect TPMS using ABS wheel speed sensors; relearn procedure after tire rotation
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
AIR BAGS:FRONTAL:PASSENGER SIDE:INFLATOR MODULE · 18V427000
2018-06-22 · EA15001
Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2005-2008 Audi A4 Sedan, A4 Avant, S4 Avant and S4 Sedan, 2007-2008 RS4 Sedan, 2004 RS4 Cabriolet, 2007-2009 A4 Cabriolet and S4 Cabriolet, 2005-2011 A6 Sedan, 2006-2011 A6 Avant, and 2007-2011 S6 Sedan vehicles. These vehicles are equipped with certain air bag inflators assembled as part of the passenger frontal air bag modules used as original equipment or replacement equipment. In the event of a crash necessitating deployment of the passenger frontal air bag, these inflators may explode due to propellant degradation occurring after long-term exposure to absolute humidity and temperature cycling.
Consequence: An inflator explosion may result in sharp metal fragments striking the driver or other occupants resulting in serious injury or death.
Remedy: Audi has notified owners, and dealers will replace the passenger frontal air bag with an alternate remedy part, free of charge. The recall began June 29, 2018. Owners may contact Audi customer service at 1-800-253-2834. Volkswagen's number for this recall is 69R7. Note: This recall supersedes recalls 16V382, 17V032 and 18V004 and includes vehicles that may have had their air bag previously replaced under one of those campaigns.
AIR BAGS:FRONTAL:PASSENGER SIDE:INFLATOR MODULE · 17V032000
2017-01-11 · EA15001
Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2009 Audi A4 Cabriolet, S4 Cabriolet, A6 Avant, A6 Sedan and S6 Sedan vehicles originally sold, or ever registered, in Arizona, Arkansas, Delaware, the District of Columbia, Illinois, Indiana, Kansas, Kentucky, Maryland, Missouri, Nebraska, Nevada, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Virginia, and West Virginia, or "Zone B."
Additionally, unless included in "Zone B" above, Volkswagen is recalling certain 2005-2008 Audi A4 Avant, A4 Sedan, A6 Sedan, S4 Avant and S4 Sedan vehicles, 2007-2008 A4 Cabriolet, RS4 Sedan, S4 Cabriolet and S6 Sedan vehicles, and 2006-2008 A6 Avant and 2008 RS4 Cabriolet vehicles originally sold, or ever registered, in Alaska, Colorado, Connecticut, Idaho, Iowa, Maine, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New York, North Dakota, Oregon, Rhode Island, South Dakota, Utah, Vermont, Washington, Wisconsin, and Wyoming.
These vehicles are equipped with certain air bag inflators assembled as part of the passenger frontal air bag modules used as original equipment or replacement equipment. In the event of a crash necessitating deployment of the front air bags, these inflators may rupture due to propellant degradation occurring after long-term exposure to absolute humidity and temperature cycling.
Consequence: An inflator rupture may result in metal fragments striking the vehicle occupants resulting in serious injury or death.
Remedy: Audi will notify owners, and dealers will replace the passenger frontal air bag inflator, free of charge. The recall began March 30, 2018. Owners may contact Audi customer service at 1-800-253-2834. Note: This recall has been superseded by recall number 18V427.
Performance
Horsepower
340hp
Torque
302lb-ft
0–60 mph
5.0sec
Quarter mile
13.5sec
Top speed
155mph
Capability & size
Curb weight
3,990lb
Wiper blades
B7 generation sedan. Some sources show 22/19 configuration.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2007 Audi S4 4.2L V8 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years.