* Distributor Cap and Rotor: Even if the wires are new, the distributor cap and rotor can have cracks or carbon buildup that disrupt the spark, especially under load when the engine demands more power. Inspect them closely for any damage or discoloration.
* Ignition Coil: The coil provides the high voltage for the spark plugs. A failing coil might struggle to generate sufficient voltage at higher RPMs. This is a common culprit for misfires under acceleration.
* Fuel Delivery: A clogged fuel filter or a failing fuel pump can restrict fuel flow, leading to misfires when the engine demands more fuel. Check the fuel pressure (ideally with a fuel pressure gauge) to rule this out. A failing fuel pressure regulator could also be a problem.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A faulty MAF sensor can provide inaccurate readings, leading to a lean or rich fuel mixture, resulting in misfires. Cleaning it (carefully, following instructions for your specific sensor) might help, but replacement might be needed.
* Oxygen Sensor: The oxygen sensor helps the engine control the air-fuel mixture. A faulty sensor can lead to an incorrect mixture, especially under load, causing misfires.
* Crank Position Sensor (CKP): This sensor tells the engine computer the position of the crankshaft. A faulty CKP sensor can cause erratic timing and misfires, especially under load.
* Vacuum Leaks: A vacuum leak can disrupt the proper air-fuel mixture, leading to misfires, especially noticeable under acceleration. Inspect all vacuum hoses for cracks, leaks, or disconnections.
* Fuel Injectors: A clogged or malfunctioning fuel injector can prevent sufficient fuel from reaching a cylinder, causing a misfire. This is more difficult to diagnose without specialized equipment.
Troubleshooting Steps:
1. Visual Inspection: Carefully inspect the distributor cap, rotor, and vacuum hoses. Look for any cracks, damage, or buildup.
2. Check Fuel Pressure: This requires a fuel pressure gauge and is best done by a mechanic if you're not familiar with the procedure.
3. Check for Codes: Use an OBD-II scanner (even a cheap one from an auto parts store) to check for any diagnostic trouble codes (DTCs) stored in the engine computer. These codes can give valuable clues. (Note: A 1993 Buick Century might not have OBD-II; it's likely an earlier system requiring a different scanner.)
4. Professional Diagnosis: If you're not comfortable with these checks, take your car to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently.
Don't just keep throwing parts at the problem. Systematic troubleshooting will save you time and money. The fact that it only misses under load is a crucial piece of information in narrowing down the possibilities.
