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Vladgmru, Automotive Electrician
Category: Cadillac
Satisfied Customers: 2667
Experience:  I've been working with American made cars since 1992.
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I have a 2006 Cadillac STS-V (supercharged Northstar, not an

Customer Question

I have a 2006 Cadillac STS-V (supercharged Northstar, not an LS engine). One of my cats became suddenly clogged last night when I was accelerating on to the highway, causing the CEL to flash and the engine to bog down and sound terrible. I still had to drive it 100 more miles in this condition, though the CEL would only flash when I got on the gas and RPMs got high enough, further pointing to a clogged cat.
His morning, it finally threw an active code. I had it scanned and in fact got a P0420 and P0300, basically confirming the clogged cat.
I found a shop that happened to be open and was willing to gut my cats. With that now done, the car is 80% better, but still seems to suffer a slight loss of power. After driving around a bit, the only codes I have are 0420 and 0430, which are of course both expected.
So, my question is, what else could have happened as a result of driving for a few hours on a VERY clogged cat? Fouled plugs on that bank maybe?
Submitted: 1 year ago.
Category: Cadillac
Expert:  Vladgmru replied 1 year ago.

Hello and welcome to JustAnswer.

My name is Vlad.

In my experience driving with a clogged catalytic converter does not do any damage, you just really usually have no power but as soon as you remove the blockage letting your engine " breath", it starts working fine.

Even if you have contaminated spark plugs, they should self clean after driving awhile on highway.

I would like to mention that engine misfiring could cause catalytic converters failure because of unburnt fuel so lit is worth to check if you engine misfired before cats failure.

Customer: replied 1 year ago.
Hi Vlad,
I understand that a misfire (or any other reason for a rich condition) could contribute to an early demise for the cats. I had no known issues or codes prior to the cat getting clogged.
I have now driven a few hundred more miles on the car, and power is still not entirely where it should be. It is too late now tonight for me to pull codes again and see if a misfire is still being detected or anything else for that matter.
The problem here is that my clogged cat HAS caused another problem. Before the cat clogged yesterday, I had no performance issues whatsoever. While it was clogged, the car of course ran awful. Now that there is nothing left of them, yet I have a varying degree of power loss. I am confident that whatever my issue is, driving on that clogged cat either caused it or it happened at the same exact time. I find the latter highly unlikely.
Expert:  Vladgmru replied 1 year ago.

Well, I would check for fuel pressure as a low pressure would cause lack of power. You should see some 55-60PSI with the key On and engine Off.

The only other thing I can thing about is some kind of heat damage caused by clogged catalytic converter. I would carefully inspect some plastic parts, make sure you have no vacuum leak etc.

Expert:  Vladgmru replied 1 year ago.

Hi I am just checking if my answer has helped you in anyway or if you might need more assistance.

Let me know how it goes.