2004 Audi S4. Consumer states vehicle failed while driving, engine, power brakes and steering locked up the dealer informed the consumer, the vehicle had suffered catastrophic engine failure, which was most likely due to the failure of the timing chain or adjusters. The consumer was quoted a price of $24,000 for the repairs. The consumer has since learned it was a relatively common problem for his model and year. The specific mechanical flaw seemed to be that the timing chain coordinated the action between the pistons and the valves. The timing chain was supported by several plastic guides. The guides pushed against the chain by the adjusters.

- Berkeley, CA, USA

Engine failure going 45mph due to broken valve spring. Faulty part documented in 5/2005 usa today but Audi will not repair.

- Mazomanie, WI, USA

See the NHTSA ODI complaints: 10267048, 10263937, 10262201, 10261864, and 10261281 my first experience with the catastrophic engine failure of the "cam chain tensioner" components was in Dec of 2008 on the bank 2 cam. Fault code "set point not reached (over-retarded)." With misfires to all cylinders on bank 2 - all but rendering the vehicle unable to drive. There was approximately 54,000 miles on the odometer. Though out of warranty I contacted Audi to no avail. I am sorely disappointed in Audi for engineering such shoddy design, and not standing by their product. In fact criswell Audi charged $300 for an ECU update that did nothing. Although the S4 is a low volume car the 4.2L engine is used in many of their products; and if this complaint venue any indication it appears to suffer a high percentage of expensive and dangerous failures. The cost to drop the engine and transmission in order to make the repair was ~$4,500.

- Ellicott City, MD, USA

See the NHTSA ODI complaints: 10267048, 10263937, 10262201, 10261864, 10261281, and 10294798. My second experience with the catastrophic engine failure of the "cam chain tensioner" components was in Nov of 2009 on the bank 1 cam. Fault code "set point not reached (over-retarded)." With misfires to all cylinders on bank 1 - less than one year from the same failure on bank 2 (see NHTSA ODI complaint #10294798). There was approximately 70,000 miles on the odometer. As I mentioned before, although the S4 is a low volume car the 4.2L engine is used in many of their products; and if this complaint venue any indication the engine appears to suffer a high percentage of expensive and dangerous failures. The cost to drop the engine and transmission in order to make the repair was another ~$4,500.

- Ellicott City, MD, USA

At 44,000 miles my car has catastrophic failure due to defective parts. It is a safety issue as I stated above because many people experience the engine revving up. The transmission can also be a safety issue because it typically happens under hard braking which all of you know if you are in gear you slow down better if all of a sudden you pop out of gear you car does not have as much holding you back.

- Dayton, OH, USA

Catastrophic engine failure and seize at 70mph. Previous the failure, Audi replaced bent valves due to timing chain tensioner failure. Less than 300 miles from new heads being installed, the engine failed completely.

- Opelika, AL, USA

I drive a 2004 Audi S4. My car suffered a major failure. The motor failed due to a design by Audi and that is unacceptable. The car failed due to these plastic guides that Audi uses as timing chain guides. The guides are never supposed to be serviced although when they fail you have to pay at least 4 thousand dollars to get them replaced because the motor needs to be pulled to replace them. They are on the back of the motor so there is no way to know when it is going to happen. When the timing chain tensioner or the guides fail it can and will result in a major motor failure. If the motor needs to be rebuilt it will cost at least $10,000. Luckily I had an extended warranty and it was covered, but I would still like to note that this is unacceptable and Audi should be doing something because this is not a failure that one would expect on a 4 year old car.

- Cranston, RI, USA

I have a 2004 Audi S4 that had catastrophic failure at only 40,000 miles due to defective parts. The car has a problem where a tensioner I am told allows the motor to rev up even when your foot is not on the gas pedal and it causes damage to the motor. This has happened to many owners, most were under warranty because this part fails at such a low mileage, in some cases under 100 miles. Not only does this cause un safe situations for the driver as the engine can have this rev up happen multiple times before the engine fails, it also causes repairs that are very very costly and not worth while. When I took my car to the dealership they also discovered that my transmission is needing to be completely replaced. This is also due to defective metals used in the syncros is what I am told. Audi has no desire to correct the problem even though they have admitted none of the problems are due to abuse but rather weak parts. Even though I am out of warranty that should not make a difference when they have had so many of the same exact cases repaired to date. My kbb value is 23,500 and the repair cost would be around $17,500.

- Centennial , CO, USA