1. Ignition System:
* Spark Plugs and Wires: These are the most common culprits. Worn, fouled, or damaged spark plugs and wires can cause misfires and hesitation. Replace them with the correct type. Don't just "gap" them; replace them.
* Distributor Cap and Rotor (if applicable): Inspect for cracks, corrosion, or worn contacts. Replace if necessary. (Some '95 Cougars might have a distributor; others may have coil packs.)
* Ignition Coil(s): A failing coil can produce weak or inconsistent sparks, leading to hesitation. Testing requires a multimeter or specialized ignition tester. A visual inspection for cracks or burns is a good first step.
* Ignition Control Module (ICM): This component controls the ignition timing. A faulty ICM can cause all sorts of driveability issues, including hesitation. Testing usually requires a scan tool or specialized equipment.
2. Fuel System:
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to hesitation, especially under acceleration. Replace it. It's a cheap and easy fix.
* Fuel Pump: A weak or failing fuel pump can't deliver enough fuel pressure, resulting in hesitation or stalling. You'll need a fuel pressure gauge to test this accurately.
* Fuel Injectors: Clogged or malfunctioning fuel injectors can deliver inconsistent fuel, causing hesitation. Cleaning them might help, but often replacement is necessary. Testing usually requires specialized equipment.
* Mass Airflow Sensor (MAF): The MAF sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can provide inaccurate readings, leading to a rich or lean fuel mixture and hesitation. Cleaning it (carefully, with MAF sensor cleaner) is worth a try, but replacement might be needed.
* Throttle Position Sensor (TPS): The TPS tells the computer the throttle position. A faulty TPS can cause incorrect fuel delivery and timing, leading to hesitation. Testing is usually done with a multimeter or a scan tool.
3. Engine Components:
* EGR Valve: The EGR (Exhaust Gas Recirculation) valve recirculates exhaust gases to reduce emissions. A stuck-open or malfunctioning EGR valve can cause hesitation. Cleaning it or replacing it might help.
* PCV Valve: A clogged PCV (Positive Crankcase Ventilation) valve can cause crankcase pressure buildup, affecting engine performance and causing hesitation. Replace it if it's clogged or stuck.
* Vacuum Leaks: Leaks in the vacuum system can disrupt the engine's operation, leading to hesitation. Inspect all vacuum hoses and connections for cracks, leaks, or disconnections.
Troubleshooting Steps:
1. Check for trouble codes: Use a OBD-II scan tool to retrieve any diagnostic trouble codes (DTCs) stored by the engine's computer. These codes can pinpoint the problem area.
2. Visual Inspection: Carefully inspect all components mentioned above for visible damage, wear, or corrosion.
3. Start with the easy fixes: Replace the spark plugs, wires, and fuel filter. These are relatively inexpensive and often solve the problem.
4. Systematic testing: If the simple fixes don't work, systematically test the other components using a multimeter or specialized tools.
5. Professional Diagnosis: If you're not comfortable performing these tests or repairs yourself, take your Cougar to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently.
Remember to always consult your vehicle's repair manual for specific procedures and specifications. Good luck!
