1. Spark:
* Spark plug: Check the spark plug in cylinder #4. Is it fouled (black, wet, or oily)? Is there a good spark? Use a spark tester for a definitive answer. Replace if necessary.
* Spark plug wire: Inspect the wire for cracks, fraying, or damage. Check for a good connection at both the plug and the distributor cap (if applicable; some 96 Tahoes might have coil-on-plug). Replace if damaged.
* Ignition coil: If your Tahoe uses a distributor, the coil might be faulty. If it's coil-on-plug, the coil for cylinder #4 could be bad. A weak spark or no spark from the coil points to a coil issue. Testing with a multimeter is recommended.
* Distributor cap and rotor (if applicable): Cracks or corrosion in the cap or a worn rotor can prevent proper spark delivery. Inspect carefully and replace if necessary.
* Ignition control module (ICM): This module controls the ignition system. A faulty ICM can affect one or more cylinders. Testing is usually required to diagnose this.
* Crankshaft Position Sensor (CKP): A faulty CKP sensor will prevent the engine from firing properly. It informs the computer about the engine's rotational speed and position.
2. Fuel:
* Fuel injector: The injector for cylinder #4 might be clogged or faulty. You'll need a fuel pressure gauge to check fuel pressure and an injector tester to verify injector function.
* Fuel pump: A weak fuel pump might not deliver enough fuel to all cylinders. Check fuel pressure at the rail.
* Fuel filter: A clogged fuel filter restricts fuel flow. Replace the filter as preventative maintenance.
3. Compression:
* Low compression: A compression test will determine if cylinder #4 is getting proper compression. Low compression indicates problems with the piston rings, valves, head gasket, or even a cracked cylinder head.
4. Other:
* Vacuum leak: A significant vacuum leak can disrupt the air/fuel mixture, affecting combustion.
* PCM (Powertrain Control Module): A faulty PCM can cause misfires. This is usually a last resort diagnosis, as it's a complex and expensive component.
Troubleshooting Steps:
1. Start with the easiest and cheapest: Spark plug, wire, and visually inspect the distributor (if applicable) and fuel filter.
2. Use a multimeter: Test the ignition coil, CKP sensor, and other electrical components as needed.
3. Get a compression test: This is crucial for determining mechanical problems.
4. Check fuel pressure: This eliminates fuel delivery problems.
5. Professional help: If you're not comfortable performing these tests or repairs, take your Tahoe to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately.
Remember safety first! Disconnect the negative battery terminal before working on any electrical components. Always consult a repair manual specific to your 1996 Chevy Tahoe for detailed procedures and component locations.
