* Ignition System: This is a prime suspect. The hard acceleration/braking/cornering stresses on the vehicle could be revealing weaknesses in your ignition system. Consider:
* Distributor Cap and Rotor: Cracks or corrosion can cause intermittent spark failure, especially under load. Inspect closely, even if they look relatively new.
* Ignition Coil: A weak coil may struggle to provide adequate spark under stress. Testing it is crucial.
* Ignition Wires: Check for cracks, fraying, or poor connections. A worn wire can cause a misfire under load.
* Pick-up Coil (in the distributor): This sends the signal to the coil to fire. A failing pick-up coil will cause intermittent misfires.
* Electrical Connections: Loose or corroded connections anywhere in the electrical system can cause intermittent problems that manifest under stress. Check all grounds, especially those near the engine and battery. Pay particular attention to connections at the fuel pump relay and the ignition components.
* Vacuum Leaks: A vacuum leak can dramatically affect engine performance, especially under load. A visual inspection is necessary but can be difficult. You might consider using a smoke machine to detect vacuum leaks.
* Transmission Issues (Automatic): If it's an automatic transmission, problems like low fluid, worn clutches, or a failing torque converter can cause stalling under load. Check the transmission fluid level and condition. A slipping transmission may manifest similarly.
* Fuel Pressure Regulator: A faulty fuel pressure regulator could be delivering inconsistent fuel pressure under load. This requires a pressure gauge test.
* Wiring Harness: While less likely, a damaged wire in the main wiring harness can cause intermittent problems, particularly under conditions that flex or move the harness.
Troubleshooting Steps:
1. Thorough Visual Inspection: Carefully inspect all components mentioned above. Look for anything out of the ordinary.
2. Ignition System Testing: This is the most likely culprit given the circumstances. A mechanic can easily test the coil, distributor, and wires with specialized tools.
3. Vacuum Leak Test: Use a smoke machine or carefully check all vacuum lines for cracks or leaks.
4. Fuel Pressure Test: Use a fuel pressure gauge to measure fuel pressure at idle and under load.
5. Transmission Check (if automatic): Check the fluid level and condition. Look for any signs of slipping or unusual behavior.
Since you've already done some work, it's time for more focused testing using the proper tools. A mechanic with experience working on older vehicles would be beneficial. The fact that there are no codes makes pinpointing the problem harder, suggesting an intermittent issue rather than a consistent fault.
