tpenta

Hello,

I recently took out the AWE muffler and cats and put on the factory ones. When I got the car back, I noticed that there is a vibration at idle that I didn't have before as if the engine is not idling proprly. If I press a little gas, the vibration goes away and smooths out.

I'm taking it back to the shop next week but was wondering if anyone knows what may be causing this.

Unfortunately, I don't know if the previous owner had done any ECU tweeks along with the AWE system.

Thoughts?

Thanks,

-Themos

docjohnM

It has been mentioned in the past that you have to pay extra-close attention to torque specs on all install hanger bolts and make sure the fit of the system is "passive". If you search the forum, I think you will see that the AWE rear muffler delete mod had some similar issues and they were easily solved

hausherrs

Did you get the stock cats from the previous owner?? I just had a cat replaced that was rattling. Almost sounded like a knocking was coming from the engine. The element in the can came loose and was banging around in the housing. If the PO replaced the stock system it might of been because the stock cat/s failed. Cost to replace 2 stock cats is rougly $4000, probably more. You can get a full exhaust with cats for less.

Steven

utkinpol

As a guess - check if steel rods you have on rear fenders do not touch mufflers at all.

If mufflers have even a slightest contact with those rods you will have plenty of kidney massage and droning inside of the car. Also what may have happened - mufflers get mounted on steel plates which have steel mesh around bolts. If you used too much force and steel mesh was compressed too much now your mufflers may transfer vibration directly to cars` frame.

rijowysock

the bolts are too tight, make sure spec is followed on exhaust, when mine was too tight, whole car shook.. loosened them to proper spec and now is fine..

tpenta

Thanks guys. I haven't taken it in yet as I've been very busy but will do it later this week.

The cats are brand new factory at $2k/side.

I suspect it's the "too tight" issue mentioned above. Interestingly, the rattling sound is only heard on cold start and only lasts until you start pumping gas. After that, it goes away and is never heard again.

Thanks,

-T

rijowysock

mine only rattled on start up idle (higher than normal) and when super hot and AC running (slightly higher idle than normal)... i was like "what the hell" and we tightened to only like 18lbs or whatever porsche said and no more problems.

hausherrs

FYI, porsche "Cost" for each cat is $1200 or so (Just had mine done at cost). Maybe leverage that to save a couple bucks.

tpenta

Thanks.

I didn't actually pay for it. The previous owner paid for it because otherwise it wouldn't pass smog.

Thanks,

-T

Mspeedster

My stock exhaust always has a loud rattle like burble noise on the driver's side on cold start up. Sounds like a baffle is loose or something. But it always goes away within 20 seconds or less and is never heard after. My dealer said it was normal and I never gave it a second thought.

Now I'm wondering if the hanger bolts are tightened to spec. Can someone verify if 18lbs is the right spec? The bolts look pretty easy to get at, I may just try adjusting the torque myself to see if it makes a difference.

Somehow looser bolts seems counter intuitive, but what the heck...

JW911

Actually they all really do that. Completely normal for about 20 seconds.

Mspeedster

Thanks. Saves me from going on a wild goose hunt and redeems my faith in the dealer.

tpenta

Perhaps we are talking about different noises. The sound I am talking about is obviously not normal. Also, the car did not sound like that with the previous cat/muffler. I'll audiotape it for you guys.

Also, the vibration is definitely not normal. I'm assuming "normal" is what my car felt like before the install.

Thanks for all the feedback, though.

-T

Mspeedster

So what are we really talking about, rattle noise or vibration? My exhaust (not the body) vibrates more at cold startup at the higher rpm, but the vibration is not felt in the car. So perhaps your vibration is caused by bolts being too tight.

The noise on the other hand might be normal for the stock cat/muffler.

tpenta

I am actually experiencing two issues:

1. There is a rattling sound coming from the left side of the exhaust system only at cold start. It goes away after a few seconds and I never hear it again.

2. There is a vibration throughout the car that exists on idle. It goes away as soon as I pump a tiny bit of gas. When on idle, the car vibrates so much that the passenger seat is vibrating hard. Yet, as soon as I pump gas, the vibration stops completely.

Before I did the installation, I had neither one of those issues. The car had no rattling sound and there was no abnormal vibration at idle.

Thanks,

-T