Audi A4 Quattro engine turns over but won't start after replacing catalytic converter and fuel injectors on Audi A4 Quattro

Some Audi A4 Quattro owners report experiencing difficulties starting their vehicle after replacing the catalytic converter and fuel injectors. These issues may stem from a weak or dead 12v battery, which can result in the engine cranking slowly or not at all. Additionally, problems with the key immobilizer system could cause the car to start briefly before dying. Owners are also advised to check the battery cables for proper connection and corrosion, as well as to consider potential water damage if the issue arose after driving through deep water. Overall, if the engine turns over but won't start, it is important to investigate these common causes and seek assistance from a mechanic or Audi dealership if the problem persists.