What are the causes of engine shaking when starting an old Jetta?
2 Answers
Old Jetta engine shaking when starting may be due to the following reasons: 1. Carbon deposits on the valves. Low engine speed causing the car to shake could be due to a dirty throttle body, which needs cleaning. 2. Fuel injector: Poor engine performance leading to engine shaking might be caused by impurities in the fuel injector affecting fuel injection accuracy, or metal additives in the fuel forming iron oxide and other metal oxides on the spark plug surface, all of which can impact engine operation. 3. Spark plug: Excessive carbon buildup on the spark plug can cause it to misfire, resulting in engine shaking.
The old Jetta engine shakes when starting, a problem I've encountered many times over years of driving. There are several key possible causes. Ignition system failure is a common issue; in older cars, spark plugs may be worn out or have excessive gaps, leading to poor ignition and uneven cylinder combustion, which causes the engine to shake. Additionally, fuel system problems such as clogged fuel injectors or insufficient fuel supply from the fuel pump can result in unstable power output during startup. Excessive carbon buildup is also a major concern, especially if the throttle body is dirty or there's carbon buildup in the intake manifold, affecting air intake efficiency and directly causing shaking. Don’t forget to check the engine mounts, as they tend to loosen and wear out in older cars, leading to increased vibration if not properly secured. Ignoring this issue long-term can increase fuel consumption and potentially damage internal engine components. I recommend first visiting a professional repair shop to diagnose the issue with a scanner, then deciding whether to replace the spark plugs or clean the fuel injectors.
