What issue might cause a gasoline engine to run fine at idle but miss under load?

A gasoline engine that runs smoothly at idle but experiences a miss under load is often influenced by various factors, and each option presented can relate to this phenomenon in different ways.

When it comes to a plugged air cleaner, this issue can restrict airflow to the engine, affecting its ability to create a proper air-fuel mixture under higher load conditions. While the engine may idle well with limited airflow, once demand increases during acceleration or when pulling a load, the engine could struggle to perform due to insufficient air intake.

The EGR (Exhaust Gas Recirculation) valve plays a crucial role in controlling nitrogen oxide emissions by recirculating a portion of the exhaust back into the intake manifold. If the EGR valve is stuck open, it may cause an excessive amount of exhaust gases to enter the combustion chamber at inappropriate times, disrupting the air-fuel mixture and leading to misfires or rough running under load despite a smooth idle.

High resistance in plug wires can also significantly impact engine performance. When ignition wires have increased resistance, they can prevent the proper voltage from reaching the spark plugs when the engine is under load. While the engine might operate adequately at idle—where the demands on the ignition system are lower—under load, the insufficient spark delivery can