Rough Sound from Engine

[rick3000]

Hi Everyone,

I was warming up my 986 for an oil change this morning, and when I exited the car I noticed a new sound coming from the engine. It is not audible from inside with the windows up, but once you are outside it almost sounds like a diesel. My '99 has 101k miles, I am thinking it could be the idler pulleys, which are some of the only components I have not changed. I installed a new water pump & belt at 95k, and the RPM's at idle are normal. I think this sound is constant, but it is difficult to hear while driving. Any suggestions/thoughts?

Link to Audio on Soundcloud

Thank you,
-Rick

[Nmbrsix]

Can you tell if it's coming from one bank or the other? Did the car throw any codes?

[rick3000]

No codes, and RPM at idle is stable. Everything appears fine, other than the sound. If I had to, I would say it is coming from the driver's side, but I can't really tell. Since I changed the oil, it appears to have gone away. The car had been sitting for about a week before today, perhaps that had something to do with it.

[Paul]

Lifter noise?

[itsnotanova]

I always suspect it's lifter noise at lower RPM's but there was a thread the other day where it turned out to be the water pump. I've also seen the alternator make the same noise. While the sound clip is great, you really need to take a closer look at where its coming from by removing the engine covers.

[rick3000]

Thanks for the replies!
I will take the engine covers off and inspect everything more closely in the next few days. After some research, I think it may have been lifter noise related to a cold start after sitting for several days. If the sound comes back, I will look into a repair.