Catalytic Converters? [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Catalytic Converters?

06-14-2007, 12:23 PM
How can you tell if your catalytic converter is stopped up? I have an 02 that has less than 100,000 on it and I don't think it should be stopped up, but it's showing a huge loss in power.

Envoy Fan
06-14-2007, 12:38 PM
Loss of power is a possibility with a clogged cat. They are still under GM warranty till 80K miles.

06-14-2007, 12:43 PM
That's good news. Is there anyway to tell if it has in fact become clogged?

Envoy Fan
06-14-2007, 12:45 PM
Any check engine light?

06-14-2007, 12:53 PM
I would think that your downstream O2 sensor would let you know... On 96 and above vehicles, ODBII should show a converter inefficiency code for a bad cat... I had a cat replaced on my previous Corvette due to a DTC... Coincidentally, the O2 sensor connection was bad and nothing was wrong with the cat that was replaced, the code reappeared after the cat replacement and didn't disappear till the downstream O2 sensor was repalced...

I also had a cat melt down on a Camaro about 10 years ago... The car had almost no power and I was getting a DTC for High Intake Air Temp... Turned out that the bad cat was building up so much pressure that it was holding the EGR valve open and causing a high temp reading on the intake air... The exhaust shop who replaced my cat did a pressure differential test on the cat... They drilled a small hole in front of and rearward of the cat and checked the pressure readings... From what I remember, more than 3-5psi differential meant the cat needed to be replaced...

06-14-2007, 02:23 PM
Thanks for the help. That's the strange thing. I'm not getting any service lights. I've had it checked for codes several times, and none were present. I had and 86 blazer back in the day that I replaced the cat on and it showed similar symptoms except it threw a code. I had a 97 Silverado that has an o2 sensor problem and it threw codes until I cleaned them up. I'm just trying to figure out why my tb is doing what it's doing without just randomly replacing parts.

06-20-2007, 02:12 PM
My Cat rattles as i accelerate. It sounds as if something has broken inside of it. Does anyone know how to contact GM about getting it warranty replaced?!? Its horrible my MPG is about 9-10mpg. WHAT CAN I DO :undecided

06-20-2007, 03:14 PM
if it is bad- the dealer should replace it under the warranty- which is 80,000 miles or something like that for this type of smog device

06-21-2007, 10:20 AM
Yep, if you're under 80,000 contact a local dealer and see about a replacement. You can check the temp in front of the converter and behind the converter. It the front is a lot hotter it's clogged. If you're over 80,000 miles and you do it yourself, disconnect the section of pipe the converter is on and drop the muffler out of the way. Remove the heat shields and slide the old cat towards the rear to remove. It's a tight fit, but it'll come out.