If your vehicle is showing engine knocking or pinging sound when accelerating on hot days, here are the most likely causes and the parts you'll need to fix each one.
Over time, carbon deposits accumulate on the pistons and valves. This raises the engine's compression ratio and creates hot spots that ignite fuel prematurely, especially under heavy load on hot days.
The knock sensor listens for the early stages of pinging and tells the engine computer to adjust spark timing to prevent it. If it fails, the engine cannot protect itself from detonation on hot days.
The EGR system recirculates a small amount of exhaust gas back into the engine to lower combustion temperatures. If the valve is clogged or fails to open, cylinder temperatures spike, causing the fuel to ping.
If the engine is getting too much air or not enough fuel due to a vacuum leak or dirty airflow sensor, the mixture burns much hotter than normal, leading to detonation under acceleration.
If spark plugs were recently replaced with ones that have the wrong heat range, the tips can retain too much heat. This acts like a glow plug, igniting the fuel before the actual spark fires.
A partially stuck thermostat or degraded coolant can cause the engine to run slightly hotter than normal. While it may not overheat on the gauge, the increased internal temperatures push the fuel to detonate.