One common problem with Toyota models with the VVT-i system controlling your engine’s timing is that of a growing rattle that becomes increasingly noticeable whenever you cold start your car nearing 100,000 miles on its engine.
Where the Rattle Comes From
Basically, here is what that rattle is about:
With the oil pressure-controlled type of VVT-I timing system, the camshaft position on the intake and exhaust valves changes via a camshaft VVT-i camshaft gear that upon signals from the car’s computer (to an oil control valve) can either advance or retard the rotating camshaft as needed under oil pressure control to ensure optimal performance over a range of RPM values. This is often referred to as “cam phasing”.
Cam phasing is possible due to a two-part adjusting camshaft gear with inner vanes against which oil pressure acts on to either advance or retard camshaft timing. There is also an oil-pressure controlled locking pin within the cam gear that places the cam gear components into either a locked or unlocked state as needed.
Cold start rattle becomes a problem when the cam gear is wearing down internally and the inner components of the cam gear are getting sloppy. For example, the vanes hitting the cam gear body from the inside. A sticking locking pin can cause rattle as well. (For an in-depth dissection of the inner workings of a cam gear used in a VVT-i system, check out this video).
In the best-case scenario, the wear is relatively mild, and you can drive your Toyota without need of immediate repair. However, in a worst-case scenario, the cam gear wear is bad enough that it grenades on you resulting in major damage to the entire timing system including the timing chain guides, the chain tensioner, the timing chain, the camshaft and the valves.
The point here is that when you begin to notice that cold-start rattle don’t panic…but don’t put off its repair too long either.
Two Mechanics, Two Videos on Toyota Engine Cold Start Rattle Problem and Fix
What prompted this topic are two YouTube videos that demonstrate a fix of a Toyota Highlander and Rav4 engine cold start timing rattle problem. The first video is an experienced mechanic who normally does not work on Toyotas but offers a watch and learn demonstration while he is learning how to do the repair on a Toyota. The second video is by an experienced Toyota expert who is doing the same repair on a similar Toyota engine with a VVT-i system.
What makes the videos interesting as a comparison is deciding whether or not the Toyota VVT-i system is a DIY repair a novice shade tree mechanic should attempt.
The first video makes this look like a possible “Yes” given that you understand the repair manual/instructions, take your time and have at least some mechanical experience.
The second video makes this look more like a definite “No” proposition because there are all these little points that if not explained in the repair manual/instructions, can lead to miserable failure