What is the correct procedure for increasing RPM or load during idle?

• A. Do not adjust RPM during idle
• B. Increase the RPM or load during the 3-minute idle period prior to tailpipe emissions
• C. Increase RPM only after tailpipe readings
• D. Increase RPM for the first minute only

Answer: (B)

During the idle emissions procedure, the engine must be brought to a defined operating condition that reflects normal driving, not just sitting at a pure idle. Increasing the RPM or load during the 3-minute idle period helps the engine warm up and reach a representative temperature and load, which stabilizes emissions readings and ensures the catalyst is operating as it would under typical driving conditions. This makes the tailpipe measurements meaningful and valid. If RPM were not raised during the idle window, readings could be skewed by cold-start or very low-load conditions. If the adjustment happened after tailpipe measurements or only for a portion of the time, it would fail to meet the standard requirement for a full, elevated idle period before sampling.