- Spark Plugs: Check the spark plugs to ensure they are in good condition and properly gapped. Worn or fouled spark plugs can cause the engine to skip and misfire.
- Spark Plug Wires: Inspect the spark plug wires for cracks, damage, or loose connections. Faulty spark plug wires can lead to misfires and rough running.
- Distributor Cap and Rotor: The distributor cap and rotor play a crucial role in distributing the electrical current to the spark plugs. If the cap or rotor is worn, cracked, or has carbon buildup, it can disrupt proper ignition and cause the engine to run rough.
- Fuel Injectors: Clogged or malfunctioning fuel injectors can disrupt the proper fuel flow to the cylinders, causing the engine to skip and hesitate.
- Fuel Filter: A clogged fuel filter can restrict fuel flow and starve the engine of fuel, resulting in rough running and skipping.
- Vacuum Leaks: Check for any vacuum leaks in the intake system or vacuum lines. Vacuum leaks can disrupt proper air-fuel mixture and cause the engine to run lean, leading to skipping and rough operation.
- Ignition Coil: A faulty or weak ignition coil can cause misfires and poor ignition. Check the coil for any damage or cracks, and test its performance if possible.
- Oxygen Sensor: A malfunctioning oxygen sensor can affect the fuel mixture and cause the engine to run rich or lean, leading to skipping and rough running.
- Fuel Pressure: Verify that the fuel pressure meets the specifications for your vehicle. Low fuel pressure can lead to insufficient fuel delivery and skipping.
- Compression: Perform a compression test to ensure all cylinders have sufficient compression. Low compression in one or more cylinders can cause skipping and rough idle.
- Mass Air Flow Sensor (MAF): If your 1987 560SL is equipped with a MAF sensor, check its operation. A faulty MAF sensor can provide incorrect air-fuel mixture data to the engine's computer, resulting in rough running.
