A car that dies at idle almost always means a dirty throttle body, a bad IAC valve, or a vacuum leak. The fix is usually under $80 and an hour of cleaning.
Carbon buildup blocks the idle bypass channel. The engine cant get enough air at idle and dies. Cleaning resolves it.
A large leak floods the engine with unmetered air. Trim cannot compensate fast enough and it stalls.
Intermittent CKP signal makes the ECU lose track of timing and the engine cuts out. Codes P0335-P0339.
Weak fuel pressure shows up worst at idle. Listen for the pump on key-on - barely audible or silent means failure.
A dead MAF makes the ECU use a default airflow value that does not match reality. Stalls under load changes.
The car dies at every stoplight, fails to restart, or you smell raw fuel. Stalling in traffic creates real collision risk.
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Idle control is harder than running - the engine depends on the IAC or throttle plate for air. A dirty IAC or stuck throttle plate fails at idle but not at speed.
Sometimes - if injectors are clogged. More often the cause is air-side (throttle body or vacuum leak) which fuel cleaner does not affect.
Indirectly. A weak battery can cause sensor voltage glitches but stalling is more often a mechanical or airflow issue.
Pull codes when the CEL is on. A scan tool that records freeze-frame data is invaluable for catching the moment of stall.
Bad crankshaft sensors and IAC valves often fail when hot. The car runs fine cold but loses signal once warmed up.