Q: When I start my car it the idle is very jumpy and the car feels like it wants to die

There are several possible causes for the idle to fluctuate like this. The most common causes are a faulty/dirty mass airflow sensor, a vacuum leak, an oxygen sensor that is reading incorrectly, or an idle air control motor that is unable to react quickly enough.

The most effective way to diagnose this situation is with a diagnostic scanner that can relay the data stream from the mentioned components in real time and compare that data to the acceptable parameters set by the manufacturer for each component.

Alternatively, you can perform physical inspections on most of the components, it just takes more time and knowledge. You can take a look at the vacuum hoses to see if there are any that have come unplugged or if the hoses have dry rotted and cracked. You will normally hear a "whistling" type sound from a vacuum leak.

You can also remove the idle speed control motor to see if there is a build up of carbon, which will keep it from being able to control the idle speed quickly enough to maintain a steady idle. There are several other possible causes for the idle to fluctuate, and if you need some help identifying the problem, feel free to contact YourMechanic to help you diagnose the rough idle and proceed with repair.