1. Fuel Delivery Problems:
* Clogged Fuel Filter: A clogged fuel filter restricts fuel flow. When idling, the engine might get enough fuel, but under load (accelerating), it starves. Check and replace the fuel filter. This is the cheapest and easiest thing to check first.
* Fuel Pump: A weak or failing fuel pump can't supply enough fuel under pressure when you accelerate. You might hear a faint whining sound from the fuel pump when the key is turned on (but before starting). A fuel pressure test is needed to diagnose this accurately. A mechanic will use a gauge to measure fuel pressure at idle and under load.
* Clogged Fuel Injectors: Clogged injectors can't spray fuel efficiently. This could cause the engine to die under load. Fuel injector cleaning or replacement might be necessary. This is more involved and often requires professional diagnosis.
* Bad Fuel: Contaminated fuel can cause similar problems. Consider the possibility of bad gas, especially if you recently filled up at an unfamiliar station.
2. Ignition System Issues:
* Ignition Coil(s): A failing ignition coil can't provide enough spark to ignite the fuel-air mixture under load. This often results in misfires and stalling. A mechanic can test the ignition coils.
* Spark Plugs and Wires: Worn-out spark plugs or damaged ignition wires can also cause misfires, leading to stalling when accelerating. Inspect and replace if necessary. This is relatively easy to do yourself.
* Distributor (if applicable): Older F-150s might have a distributor. Issues with the distributor cap, rotor, or pick-up coil can lead to similar problems. Check for cracks or corrosion in the cap and rotor.
3. Air Intake System Problems:
* Mass Airflow Sensor (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. A faulty sensor can provide inaccurate readings, leading to a lean fuel mixture and stalling. Cleaning the sensor or replacement might be needed.
* Vacuum Leaks: Leaks in the intake system can cause a lean air-fuel mixture and poor engine performance, including stalling. Inspect all vacuum hoses for cracks or disconnections.
4. Other Potential Issues:
* Throttle Position Sensor (TPS): A faulty TPS provides inaccurate information about the throttle position, causing the engine to act erratically. A mechanic can test the TPS.
* Computer Problems (PCM/ECM): In rare cases, a malfunctioning engine control module (PCM or ECM) can cause this issue. This is usually diagnosed after other simpler problems have been ruled out.
What to do:
1. Start with the easiest and cheapest: Check and replace the fuel filter. Inspect the spark plugs and wires. Look for obvious vacuum leaks.
2. If those don't solve it: Take your truck to a qualified mechanic. They have the tools and expertise to perform the necessary tests (fuel pressure, ignition system checks, etc.) to pinpoint the exact problem. Provide them with the information about the symptoms: "Idles fine, dies when accelerating."
Safety Note: Do not attempt any repairs if you're not comfortable working on vehicles. Improper repairs can be dangerous.
