EcoBoost Timing Chain Stretch

The 3.5L EcoBoost is known for impressive power and torque. It is also known for a problem that can destroy the engine if ignored. Timing chain stretch.

Unlike a belt-driven system the EcoBoost uses timing chains that are supposed to last the life of the engine. In reality the chains on the 3.5L can stretch over time especially on engines that have seen extended oil change intervals or heavy use. When a timing chain stretches it throws off the valve timing which affects performance and can eventually cause the pistons to contact the valves.

What Causes Timing Chain Stretch

Timing chains do not stretch the way a rubber band stretches. The pins and links wear slightly over time and the accumulated wear creates slack. In the 3.5L EcoBoost there are three timing chains. One primary chain from the crankshaft to the cam phasers and two secondary chains from the phasers to the camshafts.

The primary chain takes the most load and is usually the first to show wear. Oil quality plays a direct role here because the tensioners rely on oil pressure to keep the chains tight. If oil breaks down or gets thin from fuel dilution the tensioners cannot maintain proper pressure and the chains have more room to slap and wear.

Signs of Timing Chain Stretch

A rattling noise from the front of the engine especially on cold start
Check engine light with codes P0016, P0017, P0018, or P0019 (crankshaft/camshaft correlation)
Rough running or misfires at idle
Reduced power and fuel economy
In severe cases the engine may not start or may run poorly all the time

If you hear rattling and have cam phaser codes do not ignore them. Diagnosing early can save you from a full engine replacement.

Prevention

The single most important thing you can do is change your oil on a reasonable schedule with a high-quality oil. The EcoBoost is hard on oil. Fuel dilution, heat, and turbocharger demands all degrade oil faster than a naturally aspirated engine. Waiting 10,000 miles between changes with conventional oil is asking for trouble. Running a PAO-based synthetic that resists breakdown and maintaining 5,000 to 7,500 mile intervals on a tuned or heavily used engine gives the timing chain tensioners the best chance at a long life.

Repair Cost

Timing chain replacement on a 3.5L EcoBoost is not cheap. It requires removing the front cover of the engine and special tools to lock the camshafts in place. Expect $2,000 to $3,500 at a shop depending on your location and labor rates. Compared to that the cost of quality oil changes looks like pocket change.

Bottom Line

Timing chain stretch on the 3.5L EcoBoost is a real problem but it is not a mystery. The engine tells you when it is happening if you listen. Oil pressure is the lifeblood of the timing chain tensioners and degraded oil is the enemy. Keeping clean synthetic oil in the engine at all times is the best insurance policy you have against a multi-thousand dollar repair down the road.

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