A vacuum leak can cause the engine idle to fluctuate. Check all vacuum lines for cracks, looseness, or disconnection. Look closely around the intake manifold, throttle body, and brake booster for any potential vacuum leaks.
The IAC valve is responsible for controlling the idle speed of the engine. If the IAC valve is faulty or dirty, it can cause the idle to pulse or surge. Try cleaning the IAC valve with a throttle body cleaner and see if it improves the idle.
A faulty fuel pressure regulator can cause the fuel pressure to fluctuate, which can lead to a pulsing idle. Check the fuel pressure and make sure it is within specifications. Replace the fuel pressure regulator if necessary.
Worn-out spark plugs or damaged spark plug wires can cause the engine to run rough and idle irregularly. Check the condition of the spark plugs and wires and replace them if needed.
Clogged or dirty fuel injectors can cause the engine to run lean, which can lead to a pulsing idle. Try cleaning the fuel injectors with a fuel injector cleaner and see if it improves the idle.
If the pulsing idle persists after checking and addressing these potential causes, it is recommended to have your vehicle inspected by a trusted mechanic or automotive specialist to diagnose the exact problem and perform any necessary repairs.
