What Causes Low Idle and Stalling in a Camry?
3 Answers
The reasons for unstable idle speed in a Camry are as follows: Intake manifold or various valve leaks: When air, gasoline vapor, or combustion exhaust that should not enter the intake manifold gets in, it causes the air-fuel mixture to become too rich or too lean, leading to abnormal engine combustion. If the leak affects only individual cylinders, the engine will experience more severe shaking, especially impacting cold idle conditions. Excessive carbon buildup in the throttle body and intake passages: Too much carbon and dirt in the throttle body and surrounding intake passages alters the cross-sectional area of the air channel, making it impossible for the control unit to precisely regulate the idle air intake. This results in an overly rich or lean mixture and abnormal combustion. Common causes include: oil contamination or carbon buildup in the throttle body; oil or carbon deposits in the intake passages around the throttle body; and oil contamination or carbon buildup in the idle speed control motor, duty cycle solenoid valve, and rotary solenoid valve.
My old Camry had the same issue, mainly due to a dirty and stuck throttle body. The throttle seemed normal when pressing the accelerator, but at idle, the throttle plate got stuck by sludge and couldn’t close properly—the tachometer would drop below 500 RPM and then stall. Another time, it was a leaking intake manifold gasket; the mechanic found the leak using a smoke detector, and replacing the gasket fixed it immediately. Vacuum hose cracks are also common—old rubber hoses harden and develop tiny cracks, letting air sneak in. I’d suggest cleaning the throttle first—disassemble it, spray carb cleaner, and wipe around the plate. If it’s a 1997 model, pay extra attention to checking the vacuum lines.
I've been repairing Toyotas for ten years, and in 80% of cases, Camry stalling at idle is due to the idle control valve. This component is located next to the throttle body and regulates the bypass air intake. If it gets clogged with carbon deposits and seizes up, it can cause unstable RPM. Try turning on the AC when the engine is warm—if the RPM doesn't increase but instead the engine stalls without dropping speed, it's almost certainly the culprit. Also, don't forget to check the fuel pump. I've encountered several cases where insufficient fuel pump pressure caused inadequate fuel supply at idle. A dirty crankshaft position sensor can also trigger errors; you can verify this by reading fault code P0335 with a diagnostic tool.
