Posted on 9/25/2026
A car that starts and runs fine through warm weather can begin showing small ignition problems once cooler mornings arrive. The engine may crank a little longer, shake for a few seconds after startup, hesitate when you pull away, or feel rough until it has been running for a minute. Worn spark plugs are one possible reason. Cooler temperatures place more demand on the ignition system, and plugs that were already near the end of their service life have less margin left. The weather did not suddenly damage them. It simply made existing wear easier to feel from the driver's seat. Cold Starts Require a Strong, Consistent Spark When an engine is cold, the fuel mixture and combustion conditions are different from those of a fully warmed engine. The ignition system has to fire each cylinder cleanly while the engine is still stabilizing its idle and temperature. A healthy spark plug handles that job without much trouble. A worn plug can struggle to ignite the mixture c ... read more