What Causes an Automatic Transmission Car to Shake When Starting?
2 Answers
Automatic transmission cars may shake when starting due to the following main reasons: 1. Poor fuel delivery: Insufficient fuel supply at low throttle causes uneven operation among the engine cylinders, leading to shaking. 2. Damaged high-voltage wires, worn spark plugs, or a non-functioning cylinder: These issues result in unstable engine operation and shaking. 3. Dirty throttle body or excessive carbon buildup in the fuel injectors: When there is too much carbon buildup inside the engine, the fuel sprayed by the cold-start injector is largely absorbed by the carbon deposits. This leads to an overly lean air-fuel mixture during cold starts, making it difficult to start the engine. In such cases, the car only starts easily once the carbon deposits have absorbed enough fuel to reach saturation.
I used to drive an automatic transmission car and encountered starting shudder several times. It's often caused by unstable engine operation, such as when spark plugs are aged or dirty, leading to poor ignition and easy shudder during startup. It could also be due to wear in the transmission's torque converter, causing inconsistent power delivery. For a simple check, try replacing the spark plugs or cleaning the ignition coils—this usually works. Additionally, poor fuel quality can cause shudder; if the fuel is subpar, the engine will struggle. Pay attention to these issues while driving and address them promptly to avoid bigger problems, like being stranded on the roadside. I’ve also noticed that a clogged air filter makes things worse, so cleaning it regularly helps. In short, check early when you notice shudder—safety first.
