If your vehicle is showing hesitation or stumbling when pressing the gas pedal, here are the most likely causes and the parts you'll need to fix each one.
The MAF sensor measures the amount of air entering the engine. If it is dirty or failing, it miscalculates the required air/fuel mixture, causing a lean stumble when you press the gas pedal. This is often caused by over-oiled aftermarket air filters or forgetting to plug the sensor back in after an air filter change.
A weak spark struggles to ignite the denser air/fuel mixture introduced when you open the throttle, leading to a misfire and hesitation under load. Common installation errors include incorrect spark plug gap, loose plugs, or cracking the ceramic insulator during installation.
Carbon buildup inside the throttle body can restrict initial airflow, or a worn Throttle Position Sensor (TPS) can fail to tell the computer how fast you are pressing the pedal, causing a delayed engine response.
Cracked hoses or failing gaskets allow unmetered air into the engine, throwing off the air/fuel ratio and causing a stumble, especially at lower RPMs. This frequently happens if hoses are left disconnected or pinched after recent engine work.
The engine demands a sudden surge of fuel when accelerating. A restricted fuel filter or a weak fuel pump cannot deliver fuel fast enough, causing the engine to hesitate or bog down.
A severely restricted exhaust prevents the engine from breathing out. When you press the gas, the exhaust gases back up, choking the engine and causing a severe hesitation or complete lack of power.