Ignition System: This is often the first place to look in a skipping engine.
* Worn spark plugs or wires: These are the most common culprits. Inspect for cracks, corrosion, or excessive wear on the plugs, and check the wires for damage, fraying, or poor connections. Consider replacing them as a set.
* Ignition coil(s): If you have multiple coils (one per cylinder or a few per bank), a failing coil will cause misfires in the cylinders it serves. They can be tested with a multimeter or by swapping them with known good ones (if possible).
* Ignition control module (ICM): This module controls the firing sequence of the coils. A failing ICM can cause erratic firing and skipping.
* Distributor cap and rotor (if applicable): If your 350 has a distributor, inspect the cap for cracks or carbon tracking, and the rotor for wear. Replace if necessary.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the position of the crankshaft. A faulty CKP will disrupt timing and cause misfires.
Fuel System:
* Fuel injectors: A clogged or faulty fuel injector will prevent proper fuel delivery to a cylinder, leading to a misfire. They can be tested with a fuel pressure gauge and injector pulse tester.
* Fuel pump: A weak or failing fuel pump might not deliver sufficient fuel pressure, resulting in a lean condition and misfires.
* Fuel filter: A clogged fuel filter restricts fuel flow, mimicking the effects of a weak pump.
Other Potential Causes:
* Vacuum leaks: Leaks in the intake manifold or vacuum lines can disrupt the air/fuel mixture, leading to skipping.
* PCV valve: A clogged Positive Crankcase Ventilation valve can cause a buildup of pressure in the crankcase, affecting the engine's performance.
* Compression issues: Low compression in one or more cylinders can cause misfires. This requires a compression test to diagnose.
* Engine sensors: Various sensors (like the MAF sensor or O2 sensors) provide crucial data to the engine control unit (ECU). Faulty readings can lead to misfires.
Troubleshooting Steps:
1. Listen carefully: Does the skipping occur at a specific RPM range? Is it a consistent skip, or does it vary? This can provide clues.
2. Check for trouble codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs) stored in the ECU. These codes can point you towards the problem.
3. Visual inspection: Carefully inspect all components listed above for obvious signs of damage or wear.
4. Systematic testing: Test components one by one, starting with the most likely causes (spark plugs, wires, and ignition coil).
Important Note: If you're not comfortable working on your engine yourself, it's best to take your Caprice to a qualified mechanic for diagnosis and repair. Ignoring a skipping engine can lead to further damage. The cost of a misdiagnosis and incorrect repair can far outweigh professional help.
