When I start my DB8, it rattles loud enough from underneath the car.I am beginning to think that it is my Catalytic converter. If my Cat istarts going out,what symptoms do I expect?

 

if you have a bad cat it should have a CEL

the rattle could be from the heat shield hitting something... could be hangers or exhaust leak too. go check that out

in my case i THOUGHT it was my cat but it was my resonator, **** blew open and just rewelded it.

i never had a rattle ever since

or you can take it to a exhaust shop which usually may check for free

 

probably just your heat shield. put your car up on some jack stands and turn it on. go under it and listen for the rattling. wear a glove or wrap a towel around your hand and press on what ever is making the sound. if its from the heat shield or from your exhaust.

and on re-reading your post, you have a db8, how old and how many miles?

 

1995 DB8. Chassis is about 215K. Previous owner says about 110K on the 98 Swap.

I think it is a decent DB8. WIll post pics in a while.

I do have a CEL light or the Maintenance light. Near the bottom Left on the dash.

If it is the cat. I hope to get some more cash to replace it and buy some edelbrock Carb legal headers. Driving in Cali is rough...

 

yea, probably your cat. check the code, if it says o2 then more then likely your cat is gone, or you just need a new o2 and the heat shield is gone.

 

How well is your MPG? Driveability symptoms such as a drop in fuel economy, lack of high speed power, rough idle or stalling are classic symptoms of excessive backpressure due to a plugged converter.

 

The check engine and the maintenance light are two different things. BTW you can run no cat on an OBD1 car and not get a code. The O2 sensor has nothing to do with the cat on OBD1 cars. The sensor (1) is located before the cat. For the OP, like was stated by other people, check your heat shields first. I have seen resonators break up inside as well as catalytic converters. If you bang your hand against the resonator and it rattles that may be your issue as well. When looking for any issue always tackle the cheaper items first, which in this case would be the heat shields, then the resonator, then the cat. Good luck!

 

Thanks for the tip!! Can I just tighten the shield?

What will cause a Maintenance light?

 

The maintenance light comes on at scheduled intervals to remind you to get the recommended maintenance done on your car (timing belt, water pump, etc.) If you have an owner's maunal, it should be in there. Basically most people just reset it and go on with life. Is it a great idea...it all depends on what maintenance your car has had. If it's never been done maybe its time to consider a timing belt/waterpump change. Anyway just know that the maintenance light is scheduled to come on automatically at certain intervals, and the check engine light tells you if you have a certain issues that need immediate attention. As for tightening the shield...Most of the time the shield bolts become rusted, and you can't really tighten or loosen them. To be honest most people just remove them, and as long as that was the problem, the rattle of course goes away. I have never heard of any adverse effects of removing a heat shield, but I am sure someone will disagree. Good luck!

 

Did you ever figure out what the rattle was from? I had the same problem 5 months ago. When I took off my cat, there was a piece of the element in the catalytic converter that broke off and was rattling around inside the cat. I used a screw driver to break up the loose piece and get it out of the cat. Problem solved

 

Maint light is oil change reminder.
If the rattle sounds metallic it is probably a heat shield. Either tighten it or bend it back.
EDIT: Why the hell did you bump this old thread?

 

maybe I missed it but what code are you getting assuming you do have a cel and not that maintenance light.

 

At the time I had no CEL just the maintenance. NOW I do have the CEL on and off. I have no way of checking myself if the cat is bad. The I took it to a muffler place to see what they could do for me as far as a quiter exhaust. He let me look under the car and noticed the shielf is in place and not loose. He said that if my cat was blown, I would know due to the increased sound. He said that it did not look OEM. Wish I took my camera.

As for now, I am in the market of selling the system: Headers, and exhaust. Looking at spending about a 1000 to do all that and the CAT. Only thing used I am trying to get is the Header. I need to get smogged.

Funds are low but will be doing so in the next month.

 

his car is obd1 so it probably wont throw an 02 sensor code if it was bad. I have a gutted cat converter from the previous owner and no cels. Take the heatshields off the cat though, it would be my GUESS that is what your hearing rattle.