Why does the Audi A4 have a cylinder compression ratio fault with cylinder 2 not firing?
2 Answers
Some have intelligent operating modes. The content regarding the Audi A4 cylinder compression ratio fault with cylinder 2 not firing is as follows: When two out of four cylinders are not working: It indicates that the current driving power is sufficient, and the computer will assess the vehicle's power demand. When the throttle is increased: It indicates a higher power demand, and the computer will promptly analyze and activate the other two paused cylinders to start working. This is an application of new technology and a requirement for energy saving and emission reduction. Solution: For no ignition, first check the spark plugs. If replacing a new set of spark plugs doesn't work, check whether the high-voltage ignition coil has an issue. If it is confirmed that there is electrical output, it is likely a clogged direct injection nozzle. Clean the direct injection fuel line and nozzle, and replace the direct injection nozzle if necessary. If there is no electrical output, it is usually a problem with the high-voltage ignition coil. After replacing the high-voltage ignition coil, perform a matching procedure.
When an Audi A4 experiences misfiring in cylinder 2 and compression ratio issues, the cause usually lies in the mechanical components. I've handled many similar cases where insufficient cylinder pressure is often due to poor valve sealing or worn piston rings—poor sealing prevents fuel ignition. If cylinder 2 is misfiring alone, check if the ignition coil has failed or if the spark plug is severely carbon-fouled. The most extreme case I've seen was a clogged fuel injector causing an overly lean air-fuel mixture. Additionally, an unstable signal from the crankshaft position sensor can lead the ECU to miscalculate ignition timing. Prolonged neglect of this issue can even damage the catalytic converter. It's best to quickly test the pressure with a compression gauge—if it's more than 10% below the standard value, it's almost certainly an internal sealing problem.
