What are the key operating points for driving during dual-idle speed testing?

[DelRowan]

Dual-idle speed testing should avoid direct sunlight or humid environments. Key operating points for dual-idle speed testing: Avoid splashing water, chemical solvents, benzene, or gasoline onto the equipment; prevent the equipment from experiencing impacts and vibrations, perform regular maintenance, and ensure the instrument does not inhale water vapor; connections between external devices such as communication data cables and printers and this instrument must be made under power-off conditions for both sides—never perform hot-plugging; if the equipment's fuse burns out, it must be replaced with an identical model; during equipment calibration, standard gas must be used to ensure measurement accuracy; the vehicle's exhaust system must not have any leaks; do not arbitrarily turn off the power during diagnostic testing or idle speed testing; after obtaining test results, the probe must be removed and the tachometer probe detached before driving; avoid direct sunlight or humid environments. Testing equipment: Exhaust gas analyzer, flow analyzer, tachometer analyzer, OBD diagnostic tool.

[DeJohn]

I just had my exhaust emission test last month using the dual idle method. The key is to control the RPM and timing precisely. First, ensure the engine reaches normal operating temperature - just let the coolant temperature gauge needle settle in the middle position. After starting in neutral, maintain idle speed around 700 RPM for the initial reading. Then quickly press the accelerator to reach about 2500 RPM (never exceed 3000 RPM), hold steady for 30 seconds before releasing back to idle. Keep the throttle position fixed throughout - I always have a friend monitor the tachometer. The equipment will compare emission data between high and low idle states. Any steering wheel movement or AC activation during testing may cause failure.

[FranciscoMarie]

In practice, I've noticed two common mistakes. One is rushing the test without sufficient warm-up, as cold engine conditions will produce higher tailpipe emissions. The other is applying throttle too abruptly, causing RPM to spike beyond standard values. The better approach is to gently press the accelerator with the ball of your foot, gradually increasing to 2500 RPM as if stepping on cotton, then mentally counting to thirty before releasing. Remember to turn off all electrical equipment during testing, and it's best to empty the trunk of heavy items beforehand. Some drivers worry open windows affect results, but this actually matters little.

[MaryMarie]

The dual-idle test mainly focuses on the operation rhythm. After ignition, wait until the engine coolant temperature normalizes, then shift to neutral and begin recording data once the idle stabilizes. Next, smoothly accelerate to the mid-speed range and maintain a steady RPM, which roughly corresponds to the RPM range when driving at 70 km/h. The key is to make the RPM transitions decisive and avoid stalling when returning to idle. It is recommended to drive on the highway a few days before the test to clean carbon deposits, which can significantly improve exhaust emission data. Before the operation, check for any exhaust pipe leaks, as loose connections can sometimes cause abnormal data.