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Bad cat

Posted by alanrw 
April 20, 2012 12:35AM
2 years ago, I replaced the original cat on my 1984 BMW 325E. Immediately after installation, the car underwent a smog test and HC and NOX were within limits.

Last week, I was driving when a sound like an angry beehive began to eminate from under my car. I got home, got under the car, tapped on the cat with my fist and it sounds like marbles loose in there. The cat I installed 2 years ago has an 8 year warranty on it. I had the car smog tested today and HC and NOX were slightly higher but still within limits. I called the manufacturer of the cat and they are trying to tell me that something is wrong with my car, the cat must have overheated which can occur with leaking injectors or a bad muffler. Muffler was replaced with new factory unit 3 years ago. I was told by a friend who is a car mechanic if my injectors were leaking, my mileage would be pretty poor. My milage is still pretty good. Is the manufacturer just trying to dodge the warranty on this?

alan
April 20, 2012 08:47PM
Bad cat?

I have a bad cat. Every night he jumps on my car with muddy or sandy paws.

I'm hoping to get the car painted this summer, but I'm going to have to do something about that #@$% cat first.


April 20, 2012 08:51PM
Quote
Ferdinand
Bad cat?

I have a bad cat. Every night he jumps on my car with muddy or sandy paws.

I'm hoping to get the car painted this summer, but I'm going to have to do something about that #@$% cat first.


Different cat Ferd; this one is obviously an AM replacement.
I have had two AM cats replaced that failed AirCare; one in two years and the other in four years. They are made that way on purpose sad smiley
April 21, 2012 10:58AM
Should I replace the o2 sensor as part of this? How do you test an o2 on a pre obd II car?

alan
April 21, 2012 02:01PM
If there are no codes being thrown for the O2 sensor; don't worry about it as it will still be in working order and to spec.
rkj
April 21, 2012 05:01PM
Quote
Ferdinand
Bad cat?

I have a bad cat. Every night he jumps on my car with muddy or sandy paws.

I'm hoping to get the car painted this summer, but I'm going to have to do something about that #@$% cat first.


That could be a problem; cats get pretty attached to warm hoods!



Edited 1 time(s). Last edit at 04/21/2012 05:01PM by rkj.
April 23, 2012 03:59PM
Well, there are no codes on an 84. But I did find a test using a high quality DVM.

alan
April 24, 2012 11:56AM
That's what I wanted to suggest, check with a Volt meter, it should switch output level around lambda 1 (so if your car is running correctly, it should be switching constantly). If it is not switching, either the car is off or the sensor is shot.
rkj
May 02, 2012 11:01AM
Quote
Michiel 318iS
That's what I wanted to suggest, check with a Volt meter, it should switch output level around lambda 1 (so if your car is running correctly, it should be switching constantly). If it is not switching, either the car is off or the sensor is shot.

How would you check for this, and what values on the meter would you use??? Please
May 02, 2012 12:50PM
It should be switching from low level (+/- 0.2 V) to high level (+/- 0.8 V) about once a second. On a slow meter you would see a reading of about 0.45 V. If low level isn't low enough, or if high level not high enough or if the switching takes longer, the sensor's on its way out. If the level remains either high or low (no switching), the engine is running lean or rich.
May 02, 2012 05:22PM
My understanding is you need to use a good DVM, not one of the cheap ones.

alan
May 03, 2012 03:07PM
Here's a similar procedure, your DVM needs to be high impedance.
rkj
May 14, 2012 10:49PM
Thanks Michiel and Alan. Nice info to have.... thumbs up
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