Toyota Cold Start Engine Rattle Before/After Repair TSB 0041-13
2011 Toyota Rav4 brief engine rattle at cold start-up.. TSB (Toyota Service Bulletin) #0041-13 Mine was covered by power train warranty and repaired at no cost..
Possible consequences for failure to repair..Info below is from a repair forum thread on this subject..
"Bolts used to secure the variable valve timing control device can become loose, causing the vehicle to stop while being driven. Early warning for this condition can be identified as a brief rattle noise for approximately 1 second upon a cold start-up.
Description of Problem:
The subject vehicles are equipped with a Variable-Valve Timing (VVT) system which controls the camshafts to provide optimal valve timing under certain driving conditions. The bolts used to secure the housing and sprocket of the intake-side VVT gear assembly could become loose due to abnormal impacts generated within the gear assembly immediately after a cold start-up.
If this occurs, the VVT gear will not control the intake valves correctly. In certain cases, the VVT gear housing and sprocket could separate and result in the engine stopping while the vehicle is being driven, increasing the risk of a crash.'''