Which of the following is NOT a cause of engine pinging or detonation?

Retarded ignition timing is generally associated with preventing engine pinging or detonation, rather than causing it. When the ignition timing is set too late, it can reduce the combustion temperature and pressure within the cylinder, thus lowering the likelihood of pre-ignition and detonation occurring.

In contrast, a faulty EGR valve, excessive machining of the cylinder head, and using fuel with a low octane rating can all lead to conditions that promote pinging. A faulty EGR valve can limit the flow of exhaust gases that help cool the combustion process, leading to higher combustion temperatures. Excessive machining of the cylinder head can alter the compression ratio, making the engine more prone to knocking. Lastly, using fuel with too low an octane rating means the fuel may ignite prematurely under pressure, resulting in pinging.

Understanding the relationship between ignition timing and engine performance is crucial in diagnosing and resolving issues related to engine pinging.