California Smog Check Inspector Practice Test

What is the timing tolerance during an ignition timing functional test if no manufacturer's specification is available?

1. ±5 degrees

2. ±10 degrees

3. ±3 degrees

4. ±1 degree

The correct answer is: ±3 degrees

During an ignition timing functional test, the timing tolerance serves as a benchmark to ensure that a vehicle's ignition system is operating correctly, especially when no manufacturer's specifications are available. The standard tolerance of ±3 degrees is considered appropriate because it reflects a realistic range that allows for minor variances in the timing without significantly affecting engine performance. This degree of tolerance is sufficient to account for common wear and minor deviations in timing components while still indicating a properly functioning ignition system. Smaller tolerances, like ±1 degree, may not be practical considering the variability that can occur in the ignition systems of different vehicles. Similarly, broader tolerances, such as ±5 or ±10 degrees, could lead to significant performance issues and potentially raise emissions levels, which goes against the goals of a smog check. Adhering to a ±3-degree tolerance supports the overall objectives of the smog check program by ensuring vehicles remain within acceptable operational parameters, helping to minimize emissions and promote environmental compliance.