Here's why:
* IAC Valve: This valve controls the amount of air entering the engine when idling. If it's malfunctioning or dirty, it might not be allowing enough air into the engine to start properly. Pressing the gas pedal increases the airflow, bypassing the IAC's faulty regulation and allowing the engine to fire.
* TPS: The throttle position sensor tells the computer the position of the throttle plate. A faulty TPS can send incorrect signals to the computer, leading to a lean fuel mixture at idle. Giving it gas overrides the faulty sensor's signal, providing enough fuel to ignite.
* MAF Sensor: A malfunctioning MAF sensor can also provide inaccurate readings, leading to an improper fuel-air mix, especially at idle. Like the TPS, forcing more air via the gas pedal can compensate for this issue.
Less likely, but still possible, causes include:
* Fuel pump: A weak fuel pump might struggle to deliver enough fuel at idle, but pressing the gas pedal increases demand and might allow it to overcome the weak flow. However, fuel pump issues usually manifest differently (long cranking, sputtering).
* Ignition system problems: Though less likely given the gas pedal's effect, a weak spark or other ignition system problem could be exacerbated at idle and improved with a higher RPM (caused by pressing the gas).
Recommendation:
Start by inspecting and cleaning the IAC valve. If that doesn't solve the problem, then consider checking the TPS and MAF sensor. A professional mechanic can diagnose the issue with diagnostic tools far more efficiently, especially if cleaning/replacing parts doesn't improve the starting issue. These sensors often show up as codes during a scan.
