slight vibration rattle

I just had a new short block put on my 06 Legacy 2.5i after loss of mileage and power with the old one. The cat was replaced at the same time because of a small leak. The power and mileage are back but there was a slight valve tap. I had the injectors cleaned and added Lucas to the oil and the tap is better. But now I'm hearing a slight vibration/rattle after it has run for a while. It's not constant or affecting power/mileage and it's not loud like the tap was. It's mostly noticed when starting from a dead stop at lower mph. It seems to be coming from where the cat and shields are, but the shields seem tight. It's more annoying than anything, but I don't want this to be the start of a bigger problem. Any ideas?

The shields on your cat pipe are proabaly rattling, most of us cut them off once they start doing this. Your secondary cat will still function properly (heat up) if removed. If they replaced your stock shields with the new that could be an issue as they may not be on tight enough.

I was coming to post a similar (or maybe the same) issue actually. In my case, rattling is loudest from a cold start when accelerating. I have heard it while idling though. it usually calms down a bit after running for a while though. Is this the same issue?

Yes ehjhey, that is very similar. It seems to be worse when going from dead start after warming up and not as noticeable at over 40mph. And then it will go away after cooling down. I checked the heat shields and they seem tight. Sounds like it is closer to top of engine,not bottom end. Nothing I've experienced before.

Just an update to anyone who can help--the rattle seems to be in sync with the rate of acceleration. It is barely noticeable at 0-20 mph then seems to be heard from 20-40 and then fades out over 40. But if you push the gas pedal harder at a low speed, you hear it louder and at a faster rattle. Heat shields double-checked and tight. No oil loss or leaks and mileage and performance are good otherwise. Any ideas? Thanks

hows the oil? metallic flakes ? honestly, that sounds alot like my problem, and im pretty sure i have a rod knock.

No flakes,oil is fine. I just had a new short block installed last month for that problem and this is a different sound and symptom. This is more like a rattle from right in front of the steering column just inside the engine. And it's only noticable at lower speeds whereas that was noticable any time you hit the gas, even in park...

Alright I finally took matters into my own hands. I found that it actually WAS the heat shielding. As solid as it seemed when I looked at it, once I gave it a whack in frustration, I heard a slight rattle. This is obviously exponentially louder given how much a running engine/Acceleration vibrates the pipe against the shielding.

 

Solution:

Grab some hose clamps like this but Bigger. You can actually connect hose clamps to make it a big as you need.

Then find your way under your car, and (obviously) while it's cool, start hitting different spots on the heat shield till you hear even the slightest bit of rattle. Chances are that's your problem.

 

Wrap the hose clamp around the spot and make sure it's really tight. Then Presto! problem solved! (hopefully)

 

Also, you may wanna get some cutters to cut off the excess section from tightening the hose clamp, because that can actually cause rattling as well.

 

It's actually detailed in this video from Eric the car guy

 

[ame=http://www.youtube.com/watch?v=-tzQclY43IA]How To Fix Exhaust Rattles - EricTheCarGuy - YouTube[/ame]

Yeah that may be what your problem is and I can relate since I had that same issue a year ago, but I have already had my tech solder all the loose areas and that still hasn't done the job. Now I'm reading that it could even be the new cat that was just installed. Or something rubbing in the suspension...the more I read on this the bigger the mystery. Has anyone found an answer for a similar problem other than the shields that would mirror my symptoms?