Rumbling Engine

Hi. A few months ago, I bought a used 2001 Mitsubishi Eclipse Spyder w/ 120K miles on it (engine only has 40K). At first, I thought it had a tire balance issue, but recently discovered that even when I idle and rev the engine between about 2,500 and 3,000 RPM, I sometimes get a loud rumbling that vibrates the whole car. It can be quite shaky, but up until now I’ve ignored it… should I be worried?

Any abnormal noise should be investigated as something minor can become something major very quickly.

There’s really not enough information known to make much of a guess as to what this problem is.
Rumbling and vibrating could be something like an engine miss, faulty motor mount, or an out of balance engine due to someone replacing the timing belt and not timing the balance shaft correctly.

Does it seem to rev fine and run well other than this rumbling and vibrating?

How’s the fuel mileage on it?

Lastly, who says this engine has 40k miles on it; the person who sold the car? Always take things like this with a grain of salt.
Since the engine has been changed, going over all of the engine mounts and bolts might not be a bad idea.

Thanks for the reply! The car works great with no other problems: 25 mpg and a smooth ride other than this rumbling phase. The rumbling, I noticed, does seem to be a bit louder when my A/C is on… but it’s still present when the AC is off, so I’m guessing the AC isn’t the main cause. I’ve had my tires balanced twice, thinking that was the issue-which it isn’t, as found during my idling experiment.

I hope the autoshop that installed the fresh engine for the previous owner wasn’t dishonest (receipt to show), but who knows! Maybe I’ll take it in to get the motor mount and engine balance checked? I’ve sort of been ignoring it in hopes of avoiding something that may be an expensive fix. I do this with the doctor too…