Subaru Legacy: FB20/FB25 timing chain cold-start rattle

The FB-series flat-four engines used in BM/BR (2009-2014) and BS/BN (2014-2019) Legacy are known for timing chain rattle on cold starts, caused by stretched chains and worn tensioners. The dual AVCS variable cam timing system can also develop slack-related VVT fault codes when chain wear advances. The fault is documented across all FB-engined Subaru models including Impreza and Forester of the same era. Repair requires chain, tensioners and guides replaced as a set.

• Distinct rattling or slapping noise on cold start, may clear after 5 to 20 seconds
• Noise persists at idle after warm-up in advanced cases
• Check engine light with cam timing or VVT fault codes such as P0011 or P0021
• Slightly rough idle or hesitation on acceleration

1. 1

   Cold-start the vehicle and immediately listen for chain rattle from the top of the engine.

2. 2

   Note whether it clears quickly (mild wear) or persists after warm-up (advanced wear).

3. 3

   Scan for stored or pending VVT-related fault codes.

4. 4

   Check service history for oil change frequency — infrequent or incorrect viscosity oil changes accelerate chain wear.

Parts involved: Timing chain.

$1,200 to $2,400 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the timing chain or tensioners been replaced?”
• “How often was the engine oil changed and what viscosity was used?”
• “Is there any cold-start rattle before the engine settles at idle?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.