I am having the same issue with my Tacoma. And it sounds like it’s coming from underneath my truck as well. I’ve taken it a Toyota dealership more than twice and the cannot find the cause.
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Check loose heat shielding. I have a 2005 Tacoma and all of the heat shielding loosened, rattled, and I had to take all of it off
If the rattling sound occurs on start up when the engine is cold, and goes away almost immediately, it's your timing chain and it needs replacement ASAP.
Did you check for loose shielding? This is a notorious problem on these Tacomas. It makes sense that you would hear it at higher speeds and when you accelerate and not hear it when you are at a stable speed. It happened to me
I’ve looked at all the heat shields that I could access on there, but none of them are loose or anything. I don’t know if I’m missing to check others but they all look like they are tight on there.
I’ve looked at all the heat shields that I could access on there, but none of them are loose or anything. I don’t know if I’m missing to check others but they all look like they are tight on there.
Could be you have a cat starting to break up inside and you're hearing pieces rattling around inside the shell.
Not a timing chain issue. Rattle noise only occurs when I’m at cruising speeds (50MPH or so). When I’m cruising, and go to accelerate, the rattle noise occurs. After doing that a couple of times, the noise goes away. I’ve been told from an independent shop, it can be a torque converter with low fluid.
Could be over advanced ignition timing, ping. Have it checked with a scan tool.