Rep Power: 0

Hello! I have an 04 EM2 EX AT with about 95200 miles. I was curious today and decided to take my car on a long, deserted stretch of road and find its top speed. I kicked it down into D3 and gently took it to the redline and then shifted into 4th. I kept it at about 112mph for about 30s-1minute, and then let it slow back down to 70. (On a side note, it felt more stable at 115 than it did at 70...) but that went down without a hitch and I parked at home. Then, about 1-2 hours later I hopped in to make a quick trip to the store. As I put the car into drive and gave it the tiniest bit of throttle, I began hearing this weird rattling sound. I then parked the car and called my uncle. He suggested I try to diagnose it here. So, I took a long screwdriver and cupped it to my ear and deduced that the sound was not coming from by the pulley at the valve cover, and that it's not the power steering pump, but when I touch it to the alternator, the sound is definitely there and pretty loud. He says I should get it checked out by a local shop or something before I go ahead and order the part, but I decided I'd ask on here before I do so. I decided I'd take a quick video of the sound; it's not the best but you can find it below. Any help would be awesome! Thanks!

[YOUTUBE]<object width="420" height="315"><param name="movie" value=" name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/7S4o-ktrhqE?version=3&amp;hl=en_US" type="application/x-shockwave-flash" width="420" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object>[/YOUTUBE]

http://youtu.be/7S4o-ktrhqE

 
Rep Power: 518

How much oil was in it when you did the run? How old was the oil?

Sounds a lot like a rod bearing.

You need someone that KNOWS what a trashed engine sounds like to give it a listen.

You could disconnect the accessory belts to eliminate the alt/AC and PS.

You could get it rattling good and disconnect each coil one at a time to see if any makes a significant difference in the noise when you rev it. If that makes a difference, that means it is in that rod/piston/cylinder/etc. Usually a rod bearing.



HTH

 
Rep Power: 0

At 92K miles it could be alternator pulley bearing or ac pulley bearing. Pull the drive belts of and spin the pulleys by hand and shake them to check for play. You can even run the car without the belts to see if the sound goes away. But be careful, the battery is not going to last very long without the alternator charging it. You should be good for a couple of quick revs though.

And check your oil, if it's low and you were over 5K rpm for a while trying to find top speed then you may well have toasted a rod bearing.

 
Rep Power: 0

Thanks for the help! And as far as the oil goes, I have Quaker State dino oil in it, and it's getting close to time for a change (2700mi since the last one, I change every 3k-3.5k), but it's close to the top hole on the dipstick.

Anyway, it's way too intermittent to be something like a rod bearing. It definitely doesn't sound the same in the video as it does in person and it only happens at lower RPMs. You may be thinking of the rough-sounding way it revs (that it sounds a little bit like a diesel is the only way I can describe it), but I only recently realized it could need a valve adjustment. It's been like that since I got it 20k miles ago so I don't really know.

I took it to a shop and they said it was the alternator for sure though, so I'll be ordering that and a hub bearing tonight!

 
Rep Power: 193

Honda recommends the valves be adjusted every 100k so that shouldn't be the issue.

If you wanna make sure it's the alt just take the belt off and start it up.