i am noticing a major loss of power at higher RPMs (3500+) and am leaning towards a clogged cat. In Park if i rev the engine a little then when i let off a hear a crackling kinda noise coming from the cat area. I didnt see and exhaust leaks or movement in the system. Am i on the right track here in thinking its the cat? Its a 3.8l with 160000km on it and it does fall into the VIN range that the clogged cats happened on. I went to a dealer today and they told me because no CEL is on and it is running fine when im not accellerating hard its not the cat... any help is appreciated.

 

In most cases the dealer has no clue about anything. I have heard plenty of cases that a clogged cat did not trip a CEL light. I would go to a local small muffler shop and have them no a back pressure test. They make a small hole before and after the cat and check to make sure it is flowing through. Do you ever notice a bad smell coming from your car? That is another sign that your cat could be bad. Your best best is to go to a muffler shop and maybe even have them repair it and then get paid back by GM. Hope this helps. If you have anymore questions feel free to ask because i had the same problem and got it fixed.

 

Could definitely be a clogged cat- could be alot of things. If you suspect the cat, things to check include:
- Any "rotten egg" smell coming from the exhaust?
- Drive it hard at night- does the catalytic converter heat up/glow red?
- If you tap the catalytic converter with a rubber mallet, do you hear any "marbles in a tin can" type noise?

If "yes" to any of the above, the cat is probably bad. If no, you might want to check other things. When was the last time you had a tune up and maintenance done? Particularly- spark plugs and wires, cleaned your MAF sensor, replaced the front O2 sensor, replaced the fuel filter, and changed the oil? The vehicle may just need routine maintenance.