Hard Start / Starts Then Dies on Cold Engine
The engine starts but stalls immediately when cold, indicating a fuel or air delivery issue that prevents the engine from maintaining idle. This is often caused by a failing fuel pressure regulator, a dirty throttle body, or a faulty coolant temperature sensor.
Diagnosis Details
Possible Causes
Failing fuel pressure regulator or weak fuel pump – allows fuel pressure to drop after shutdown, causing lean condition on cold start.
Dirty throttle body or idle air control valve – carbon buildup restricts airflow at idle when cold.
Faulty engine coolant temperature sensor (ECT) – sends incorrect cold-start enrichment signal to ECU.
Related OBD-II Codes
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What You Should Do
Check fuel pressure at the rail during a cold start (should hold pressure).
Inspect and clean throttle body and idle air control valve.
Test ECT sensor resistance and compare to specs.
Scan for diagnostic trouble codes even if check engine light is off.
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.
