What problem does too much or too little O2 indicate during combustion?

Too much or too little oxygen during combustion leads to bad combustion. The combustion process relies on the optimal air-to-fuel ratio to achieve efficient burning of the fuel. When the oxygen levels are imbalanced, it can result in incomplete combustion or excessive combustion, which produces undesirable byproducts such as carbon monoxide, unburned hydrocarbons, and nitrogen oxides.

In scenarios with too little oxygen (a rich mixture), combustion may be incomplete, leading to increased emissions and reducing the overall efficiency of the engine. On the other hand, too much oxygen (a lean mixture) can cause the combustion temperature to rise dramatically, potentially damaging engine components and also leading to increased nitrogen oxide emissions.

As a result, maintaining the correct oxygen levels is crucial for ensuring that combustion is effective and efficient, which is why this issue directly correlates to bad combustion.