Clogged Cat Symptoms?

[BLACK'98DSM]

I have the downpipe off right now, so the cat is easily accessible. I was wondering what the symptoms of a clogged cat are so that I can decide if I need to pull it or not?

- Thanks

 

[rabenne]

reduced flow, probably would get really hot, lack of power if the flow is really reduced.

do you suspect issues with it? I believe those factory 420a car's cats go for about $90 salvage.
If you have a reason to pull it, and no issues with the codes it might throw, go for it.

if you dont suspect an issue, I would say just run it as is. It probably wont gain you much in terms of power (unless your a boosted nt?)

 

[BLACK'98DSM]

I would most likely pull it to unclog it, and then replace it.

The reason I asked is because it does get very hot. As I'm under the car I noticed that the downpipe and catback are both already cooled off, but the cat is still super warm. And when I pulled the downpipe a strong smell came from the cat.

 

[dsmcrzy]

Tap on the cat with something metallic. If it sounds hollow, then it’s not clogged. If it sounds solid, it’s clogged.

 

[BLACK'98DSM]

I can see the netting, it looks clean. Thanks guys.

 

[smbgsx]

I know this was solved, but for future reference you can check for plugged exhaust/cat with a vacuum gauge. Typical manifold vacuum at idle is 17-20 In/hg. If you throttle up to 2,500 RPM with no load applied (in neutral) vacuum will settle to about that same point after a second.
If you hold 2,500 RPM and the gauge vacuum begins to fall you have a restriction. But keep in mind other variables can effect manifold vacuum such as ignition timing. You can also build a backpressure gauge from an old O2 sensor. Anything over 1.25 psi of pressure would indicate a restriction.
If the engine just plain won't start and you truly think it's a restriction issue, typically you can just remove an o2 sensor and fire it right up too.