Fuel System:
* Clogged Fuel Filter: A dirty fuel filter restricts fuel flow, leading to rough idle and power loss, especially under load (high speed).
* Fuel Pump Weakness: A failing fuel pump might provide insufficient pressure, especially at high RPMs, causing power loss and potential stalling.
* Clogged Fuel Injectors: Clogged injectors prevent proper fuel delivery to the cylinders, resulting in rough running and power loss. This is a common issue on older cars.
* Low Fuel Pressure: This could be due to any of the above issues, or a leak in the fuel lines.
Ignition System:
* Worn Spark Plugs/Wires: Old, worn, or fouled spark plugs and wires can cause misfires, leading to rough idle and power loss.
* Distributor Cap/Rotor (if applicable): Cracks or corrosion in the distributor cap and rotor can interrupt the spark delivery, causing similar issues. The Aspire might or might not have a distributor, depending on the engine.
* Ignition Coil: A weak or failing ignition coil won't provide sufficient spark energy to ignite the fuel-air mixture reliably.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational speed. A faulty CKP can cause misfires, stalling, and erratic running.
Air Intake System:
* Mass Airflow Sensor (MAF): A faulty MAF sensor provides incorrect information to the engine control module (ECM), leading to a lean or rich fuel mixture and poor performance.
* Vacuum Leaks: Leaks in the intake manifold or vacuum lines can disrupt the air/fuel mixture, causing rough idle and poor performance.
* Dirty Air Filter: A severely clogged air filter restricts airflow, leading to poor performance and potentially stalling.
Other Possibilities:
* Throttle Position Sensor (TPS): A faulty TPS gives the ECM incorrect information about the throttle position, leading to poor idle and performance.
* Engine Control Module (ECM): While less likely, a failing ECM can cause a wide range of problems, including those you've described.
* Oxygen Sensor (O2 Sensor): A malfunctioning O2 sensor prevents proper feedback to the ECM, leading to incorrect fuel mixtures and poor performance.
Troubleshooting Steps (in order of easiest to hardest):
1. Check the basics: Start with the easiest and cheapest: Inspect the air filter, check the fuel level, and visually inspect spark plug wires for cracks or damage.
2. Check for codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the ECM. This will give you a clue about the most likely problem area.
3. Fuel pressure test: A mechanic can perform a fuel pressure test to determine if the fuel pump and injectors are delivering sufficient pressure.
4. Ignition system check: Inspect and/or replace spark plugs and wires. If applicable, inspect the distributor cap and rotor.
5. Vacuum leak check: A mechanic can use a smoke test or vacuum gauge to detect leaks in the intake system.
Important Note: Without a proper diagnostic scan and potentially some further testing, it's impossible to pinpoint the exact cause. It's best to take the car to a qualified mechanic, especially since multiple symptoms suggest a more involved problem than a single faulty component. The age of the vehicle also increases the likelihood of multiple failing components.
