clogged or bad cats?

C

cackster

Member
Location
NYC
Name
John
Hello! So, what is the best way to tell if my cats are clogged? I do feel the car has to pull a lot more than it used to which makes me think there is an exhaust restriction. I checked the temp with an IR thermo before and after the cat. Before reads about 430 at operating and after reads about 100 degrees F less... Does that mean my cats are clogged? This was at operating temp. Thanks guys!

UPDATE: I did vacuum test and the pressure starts at 20 Hg and then it slowly climbs as I apply throttle( slowly).. I'm guessing that if I had a restriction, I'd notice a drop in pressure? thanks guys... I could never be a mechanic.
 
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Well the outlet should be hotter than the inlet since that's how they work. So if yours is 100 degrees less on the outlet, that may be a problem. That's a pretty severe drop though, so I would check again. It would have to be really clogged to cause that kind of restriction, I'd think you'd throw a code.

Vacuum should be -20hg since unless you're boosted, it will not go positive. It should rise closer to 0 as you open the throttle. I think the test for exhaust blockage is to rev it up to like 2k or 2500 and hold. It should rise as you open the throttle and then go back down a little at constant throttle. If it doesn't drop back down, you may have an exhaust blockage.
 
clogged cats give off sort of a rotten egg smell after driving really clogged cats turn red from all the heat being held in.
 
shadow191 said:
Well the outlet should be hotter than the inlet since that's how they work. So if yours is 100 degrees less on the outlet, that may be a problem. That's a pretty severe drop though, so I would check again. It would have to be really clogged to cause that kind of restriction, I'd think you'd throw a code.

Vacuum should be -20hg since unless you're boosted, it will not go positive. It should rise closer to 0 as you open the throttle. I think the test for exhaust blockage is to rev it up to like 2k or 2500 and hold. It should rise as you open the throttle and then go back down a little at constant throttle. If it doesn't drop back down, you may have an exhaust blockage.
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It starts at 20, and then it slowly goes up to 25 as I rev up the engine, slowly... Could this mean that my throttlebody is shot and the butterfly isn't opening or something? I don't know what would cause an intake obstruction? I mean, the car seems to pull and drive fine, but it is eating a LOT of gas. I don't spell anything, car idles fine, and I get good MPG on the highway. I pulled off the throttlebody today and I see it's completely black all around it and I see the grooves of where it should sit, but it seems misaligned. Also, I stepped on the pedal for my dad to see inside the throttle body, but the burtterfly didn't move...Does the car need to be on for that to work? Or could it be stuck?
 
That seems normal. Doesn't sound like you have an obstruction. Honestly if the cats go, you should throw a code. The O2 sensors are pretty accurate.

And unless the 45 is different, it has electronic TB so it won't move unless car is on. No cable.
 
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