Strange rattle / rumbling noise when acceleration (cold start)

Maintenance/Repairs
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1

It sounds like its coming from the engine but I could be wrong since the sound is very deep and difficult to pinpoint. I can feel the rumbling / vibrations inside the cabin itself. It only happens when accelerating.

Funny enough, after about 10 minutes of driving the rumbling noise goes away.

Has anyone experienced this before? Car is a 2014 civic lx automatic with close to 100k miles.

I’ve done most of the general maintenance items which include:
Transmission fluid
Oil changes
Spark plugs
Break pads
Battery replaced this year

Unsure if this is related as it occurred around the same time, but the right side of my headlights (low beam) will not fire on immediately. I will have to wait about 5 minutes and it mysteriously starts working again. This happens everytime I start my car. Might be related but could also just be a failing relay harness for the bulb.

2

I wonder if it’s something loose or broken in the muffler, perhaps a heat shield.

That would explain why the sound goes away after the engine warms up.

1 Like
3

Thank you for the suggestion. I will take a look tomorrow to see if I can replicate the sound.

However, the sound seems to come from the front of the car. The muffler itself is stock and hasnt been touched at all.

4

Stock mufflers go bad everyday (smile). It happens.

Good luck.

5

Most engines have a heat shield under the hood, in addition to heat shield(s) on the exhaust system.

6

You could leave it at a shop overnight and let them analyze it. I have my doubts that a heat shield would cause this.