I was able to get the loud idle to quiet down after accelerating very quickly on an empty country road yesterday - just took it up to 65 very quickly and it went back to it’s nice almost silent idle. But I know it will come back after the next day of steady rain. If this was a crack in the exhaust manifold, wouldn’t the noise come back after everything cooled off again? It is still running quietly today.
You should have gone back to your original post and entered this there:
Yes, if the manifold had a small crack that gets quiet when hot it should go back to being loud once it is cool.
You need to get the car in front of a mechanic when it is idling loudly. Someone has to figure out exactly what is making the noise.
You still haven’t described what the sound is like. “Loud” doesn’t say much.
Sorry - I don’t know how to use the forum yet. It sounds like a truck is sitting next to my car - that’s what I thought when I first heard it, but then I drove away and parked at the store and found it was my car. I can hear all four cylinders - sort of sounds like when your heart is pounding when you are scared! It usually is almost silent. Now that the sound is gone, it is idling at a lower rpm - more like 500 instead of just under 1000.