High-Probability Causes:
* Ignition System Problems: This is a very common cause for both poor acceleration and rough idling. Check these components:
* Spark Plugs and Wires: Worn, fouled, or damaged spark plugs and wires prevent proper combustion. Replace them if necessary – they're relatively inexpensive.
* Distributor Cap and Rotor (if applicable): Cracks or corrosion in these components can disrupt spark delivery. Inspect for damage and replace if needed. (Note: The 2.2L may or may not use a distributor depending on the specific engine configuration. Some used a coil-on-plug system).
* Ignition Coil(s): A failing coil(s) won't produce enough voltage for a strong spark. Testing is usually required to diagnose a faulty coil.
* Ignition Module (or PCM): This controls the ignition timing and spark delivery. A faulty module can cause erratic ignition and poor performance. This often requires professional diagnosis.
* Fuel System Issues: Problems here directly impact engine power and smoothness:
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to poor acceleration and potentially a rough idle. It's cheap and easy to replace.
* Fuel Pump: A weak or failing fuel pump can't supply enough fuel under pressure. This will usually show as poor acceleration, especially under load.
* Fuel Injectors: Clogged or malfunctioning injectors can cause a misfire and rough idle. Cleaning or replacing them might be necessary. A fuel pressure test is needed to properly diagnose this.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle position. A faulty sensor gives the computer bad information, leading to poor performance and rough idling.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor will cause the computer to supply the wrong air/fuel mixture, leading to poor performance and a rough idle. Cleaning it might help; replacement is often necessary if cleaning doesn't fix the problem.
Medium-Probability Causes:
* Vacuum Leaks: Leaks in the intake manifold or vacuum lines disrupt the engine's air/fuel mixture. This often causes rough idling and poor performance. Inspect all vacuum hoses for cracks or damage.
* PCV Valve (Positive Crankcase Ventilation): A clogged PCV valve can cause crankcase pressure buildup, affecting engine performance and potentially leading to a rough idle.
Low-Probability Causes (but still possible):
* Catalytic Converter: A severely clogged catalytic converter can restrict exhaust flow, reducing engine performance. You'd likely notice other symptoms as well (e.g., decreased engine braking).
* Engine Compression: Low compression in one or more cylinders can result in poor acceleration and a rough idle. A compression test is needed to diagnose this.
Troubleshooting Steps:
1. Start with the easy and cheap stuff: Check the spark plugs, wires, fuel filter, and visually inspect all vacuum lines.
2. Use a code reader (OBD-II): This can identify any trouble codes stored in the engine control module (ECM), pointing you toward specific problem areas.
3. Professional diagnosis: If you're not comfortable working on your car, take it to a qualified mechanic. They have the tools and expertise to diagnose more complex issues.
It's crucial to tackle these potential problems systematically. Don't just replace parts randomly; proper diagnosis is key to a successful repair.
