We see a lot of Prii in the shop, and one of the most common complaints we get from 2010+ Prii, Plug-in, and V owners is about the startup engine rattle after a cold soak.
The condition is usually caused by condensation building up in the intake, leading to partial cylinder misfires as the condensation works its way into the engine. While it does not harm to the engine, the accompanying loud rattle out of the hybrid transmission is cause for alarm and can be embarrassing to the owner. Up until April 21st, Toyota offered a redesigned intake manifold (part number 17120-37054) that made the condition much more rare (but didn’t eliminate it entirely). Here’s what an older version of that bulletin looked like. The bulletin was updated futher to include 2012-2013 models. Another bulletin for a no-start condition (codes P2111 and P0A0F) was later released that updated the intake manifold further (part number 17120-37091).
As of April 22nd, the original bulletin is declared obsolete by Toyota. Here’s what the bulletin looks like now. The reason for this is unknown at this time.
So what is a Prius owner to do?
CARspec continues to recommend replacing the intake with the most current version of the manifold for this condition. On both of the shop vehicles (a 2011 Prius and 2014 Prius Plug-in), the updated manifold has dramatically reduced the frequency and severity of the rattle, especially in cold weather. While not perfect, it makes a big difference.
Owners can help prevent the issue by letting the vehicle warm up fully before shutdown, occasionally accelerate briskly (when safe), and have the intake manifold inspected for excessive oil and water buildup below the throttle body. There is no doubt that Toyota continues to investigate the issue and we here at CARspec want to support them in helping resolve this concern.
As we learn more we’ll update the blog.