* Fuel System Problems: This is a very likely culprit. Possible issues include:
* Clogged fuel filter: A dirty filter restricts fuel flow.
* Faulty fuel pump: A weak or failing fuel pump can't deliver enough fuel under pressure.
* Clogged fuel injectors: Dirty injectors prevent proper fuel atomization. This is a common issue on older vehicles.
* Low fuel pressure: This could be due to any of the above issues or a leak in the fuel lines.
* Bad fuel: Contaminated fuel can cause all sorts of problems.
* Ignition System Problems: The spark may not be consistently strong or timed correctly:
* Worn spark plug wires: Cracked or damaged wires can cause misfires.
* Faulty spark plugs: Worn or fouled plugs are a frequent cause of this type of problem.
* Ignition coil problems: A failing ignition coil can lead to inconsistent sparking.
* Distributor cap and rotor (if applicable): These components can become worn or corroded, affecting spark delivery. The '97 Explorer might have a distributor, depending on the engine.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A faulty MAF sensor can cause a lean or rich fuel mixture, leading to hesitation and sputtering.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle position. A faulty TPS can lead to incorrect fuel delivery.
* Oxygen Sensor (O2 Sensor): This sensor monitors the exhaust gases to help the computer adjust the air-fuel mixture. A failing O2 sensor can result in a poor mixture.
* Vacuum Leaks: Leaks in the vacuum lines can disrupt the engine's performance, causing rough running and hesitation.
* Computer Issues (PCM/ECM): While less common, a failing computer can cause erratic engine behavior. This is usually diagnosed *after* other more likely culprits are ruled out.
Troubleshooting Steps:
1. Check the basics: Start with the easiest things to check: fuel level, look for any obvious leaks, and visually inspect spark plug wires for damage.
2. Check engine codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the vehicle's computer. These codes can often pinpoint the problem.
3. Systematic approach: Address the most likely issues first (fuel filter, spark plugs, wires).
4. Professional diagnosis: If you're not comfortable working on your car, take it to a qualified mechanic for diagnosis and repair. This will save you time and potentially money in the long run, preventing further damage.
Without more specific information about the symptoms (e.g., when it hesitates, under what conditions), it's impossible to give a more precise diagnosis. The above list covers the most likely causes, but a professional mechanic will be able to pinpoint the problem more effectively.
