While driving through a tunnel today I noticed a metallic rattling noise upon acceleration. It goes away immediately when I let me foot off the gas and when I park the car and rev the engine the sound does not occur. A few days ago, I had to rapidly accelerate and it felt as though I lost power for a split second. I am not sure if these are related, but I am hoping its not some sort of transmission issue (unless that is covered under the hybrid warranty Has anyone had a similar issue? If so what was the diagnosis? Regards, Matt EDIT: Oh lawd, upon... not up on. It has been a long day.
Would it be engine knocking? There are several recent posts about knocking with high temps, and different grades of gas. It will mainly occur under load. Can you hear the noise when running on electric mode only, as in going down a hill with only enough acceleration that the engine does not turn on?
Rattling upon acceleration: I've had this issue. After much searching and even watching WEBER Auto put the transmission together, I came upon the theory of the DAMPER (Part# 31270-47060) (>$900 at dealer)between the engine and transmission. It Usually occurs during slight acceleration, and just when it starts to decelerate. But eventually it occurred even at idle, with not particular events to narrow down the cause. So I decided to pull the ICE (engine) from the car, since it is much easier than the transmission IF my theory was correct. (If the theory wasn't correct, then I was just that much closer to replacing the transmission) As soon as the engine separated from the transmission and little bits of metal started falling out, we knew the theory was correct. It was indeed the Damper plate between the engine and transmission. If the forum will allow, I will post video of the distinct sounds that are tell-tales. First there is the slight clunk/click as the engine is running when switching from forward to reverse. This SHOULD have alerted me right off that the springs weren't there. Second there is the rattle upon acceleration. This was the first sound noticed by the driver that something was amiss. Third there is the constant ratcheting sound, very similar to when you are using a battery powered drill with a clutch(when the drill clutch starts to do it's job and lets loose). I was unable to post the videos (.mov format), but there is a youtube video: "prius rattle vibration sound clutch dumper transmission" that has the sounds you may recognize.
