Hard to Start or Won't Start – Starts Then Dies (Cold Engine)
The engine starts but dies immediately when cold, indicating a fuel, air, or sensor issue. Common causes include a failing fuel pump, faulty engine coolant temperature sensor, or vacuum leak.
Diagnosis Details
Possible Causes
Failing fuel pump or fuel pressure regulator – may not maintain pressure when cold, causing stall after start.
Faulty engine coolant temperature sensor (ECT) – sends incorrect signal to PCM, causing overly rich or lean mixture on cold start.
Vacuum leak (intake manifold gasket, PCV hose) – leans out mixture, causing stall when cold.
Idle air control valve (IAC) or throttle body carbon buildup – restricts airflow at idle, causing stall after start.
Weak battery or poor electrical connections – voltage drop can cause PCM to reset or fuel pump to lose prime.
Related OBD-II Codes
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What You Should Do
Check fuel pressure at the rail (should hold prime).
Scan for diagnostic trouble codes (DTCs).
Inspect ECT sensor readings with a scan tool.
Look for vacuum leaks using smoke test.
Clean throttle body and IAC if applicable.
Test battery and charging system.
Related Repairs
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
