How does the idle speed of an engine work?
At higher speeds more air is allowed through the engine to control pumping losses and drag. The actual amount of dashpot airflow must be reduced over time for the engine to return to idle. This table slows the rate of reduction as speeds decrease to provide a gentle return to idle speed without stalling.
When does a car speed up or slow down?
As the car moves towards a stop sign it will slow down. When a car moves away from a stop sign it speeds up. The concept and the graph analysis are challenging for many if not most students taking higher level math. This example shows how instructional strategies are not simply for students who struggle with math.
What should idle speed be after camshaft change?
There is no reason to simply increase idle speed from 800 rpm to 1,000 rpm after a camshaft change when a little extra calibration time allows the engine to be stable at 850 rpm. Careful control of fuel delivery, airflow mapping, and spark compensation are the keys.
What can I do to make idle speed more stable?
Reinstalling the IAC harness lead should result in a more stable idle. This prevents the IAC from leaning to either a fully open or closed static position. The object is to get the IAC motor in the middle of its adjustment range so that it has maximum flexibility to adjust airflow either up or down.
What makes a car idle at low rpm?
The engine RPM proportionately fluctuates with the speed of the car. Idle vehicles with an RPM rate signaling below 600 RPM are called low RPM vehicles. The IAC (Idle Air Control) valve is responsible for the engine’s idle speed and keeps it constant.
Why does idle speed drop during cold startup?
If the idle air control valve did not compensate for these, the idle speed would drop when certain accessories are used. In severe cases, the engine may even stall. The idle air control valve is most important on a cold startup. Problems with the idle air control will be most obvious during this time.
What does it mean when your car is stalling at idle?
Problems with idle speed —things like slow idle, fast idle, rough idle, or stalling after idling for a few seconds—are symptoms that something is wrong with your engine. These should be investigated, diagnosed, and repaired as soon as possible.
What to do when your car engine is idling?
Idling issues can be frustrating, but with some patient troubleshooting, you’ll have a real chance at figuring it out. Remember to always check your engine idle with the air conditioning and defroster turned off, as both of these systems are designed to change the idle when they are on due to the demands they place on the engine.