Why does the Jetta jerk when starting cold as if not getting enough fuel?

[DelIan]

Here are the reasons why the car jerks when starting cold as if not getting enough fuel: 1. Low engine temperature: Especially during cold starts in winter, the temperature inside the engine is insufficient, and both fuel and lubricant temperatures are low. Therefore, more fuel needs to be injected during cold starts to meet power requirements. Poor fuel atomization at low temperatures leads to reduced ignition energy, affecting power performance and causing the car to shake. 2. Carbon deposits in the engine and intake manifold: Carbon deposits can absorb a certain amount of fuel, causing the ECU to make incorrect judgments. For example, if the computer controls the injection of 100 units of air-fuel mixture but only 90 units actually enter the cylinder (with 10 units absorbed by carbon deposits), even if the remaining 90 units burn completely, the required power performance won't be achieved, inevitably resulting in shaking. 3. Ignition system failure: Aging of the ignition system weakens ignition energy, causing the ignition coil or spark plugs to fail to ignite continuously or resulting in intermittent ignition. This discontinuous power output leads to jerking during acceleration. Therefore, regular maintenance and replacement of the ignition system are crucial. If spark plugs fail while driving, it can easily cause engine misfire, severely affecting the engine's lifespan.

[JeffreyLynn]

I've also experienced the jerking issue when starting my Jetta in cold weather, which feels like the fuel isn't getting through properly. This could be related to the fuel pump's reduced efficiency at low temperatures – when it's cold, the pump turns slower, leading to insufficient fuel supply and causing jerking. Another possibility is a clogged fuel line, where a dirty fuel filter restricts flow. Worn-out spark plugs are another common culprit, as weak sparks during ignition can cause engine shaking. I'd recommend first checking the fuel pressure to confirm the pump is working properly; replacing the spark plugs is an easy fix that often helps. Cleaning carbon buildup from the throttle body can also improve airflow. For older Jetta models, fuel pump issues are more likely to occur. A temporary solution might be to let the engine idle in neutral for about 30 seconds before parking. While this seems like a minor issue, prolonged neglect can damage the car, so it's best to address it sooner rather than later.