Cat convertors or muffler

Tahoe power declined this week, noticed not a lot of exhaust coming out of the tailpipe, so I figured that since I have 100k the converters were plugged. Took the Tahoe to Midas, the pre cat temp was 360, after cat temp was 325 and the pre tail pipe temp was 160. The tech told me that he thought the cats were okay and that the muffler was clogged. Suggested that I replace the muffler. Okay, if the muffler is clogged, what clogged it? There is hardly any exhaust coming out of the muffler so, I'm gonna cut it off tonight and see if that helps. Any thoughts on the Catalytic converters? Should I go ahead an replace them ($683) welded in place or ($1300) new y-pipe?

the cat converter can get plugged but at 100,ooomi this would not be common ....

coolant entering the combution chambers will damage the O2 sensors and cause cat failures ...

question is is it the exhaust ???remove the O2 upsteam sensor on one side and with the hole open test drive ..then repeat this on the other side . see if you get the power back ...lets say no difference , then you go through the fuel pump pressure testing proceedure ...this usually causes loss of power and no check engine codes..a plugged cat/exhaust usually causes codes and other issues ...


another test is to start the cold engine then crawl under vehicle and with a hand on each cat converter see if they get hot at the same time / rate if so they are good ..if one only gets hot then the cold cat is defective...

I will try the cold start method tomorrow morning. I'm not going to drive it this weekend, just trouble shoot and see if I can find the problem. With 100K, I'm really thinking about just getting the whole exhaust system replaced, but that's money I don't have. Just replacing the cats are going to put a huge dent in my pocket. But that's why I have a garage and some wrenches.

I will try the cold start method tomorrow morning. I'm not going to drive it this weekend, just trouble shoot and see if I can find the problem. With 100K, I'm really thinking about just getting the whole exhaust system replaced, but that's money I don't have. Just replacing the cats are going to put a huge dent in my pocket. But that's why I have a garage and some wrenches.

I live in the rust belt ..my 2000 5.3L the exhaust is original ..still looks good over 125,ooomi. ...don't spend money you don't have on parts not defective...muffler shops are good at replacing mufflers NOT troubleshooting these vehicles !

follow the recommended steps then open the wallet ..

Goto a local parts store and get a back pressure tester. They are fairly cheap. Remove your O2 sensors and measure both banks. Anything over a pound and a half of pressure is clogged. Or just do what j Cat said and take Sensor 1 on your drivers side and passenger side (do one at a time) and test drive it, if the power seems better they are clogged.

Usually with a clogged cat you get misfires on all the cylinders that on the clogged converters side and you get a P0420 DTC Cat low effiency. Clogged converters are caused by lean condition, Cats are killed they cant committ suicide.

Remember.
A good old fashion engine vacuum gauge test will show restricted exhaust and also a lot other problems.
If engine vacuum reading is less at 2k RPM THAN IDLE YOU HAVE RESTRICTED EXHAUST.
Cat back pipe needs to be undone to check for back of cat restriction.

Thanks for everyones assistance. Cats are fine, O2 sensors on bank 2 are failing. Will tune up with AC Delco plugs, replace O2 sensors (all 4) and fram fuel filter on Monday.

Thanks for everyones assistance. Cats are fine, O2 sensors on bank 2 are failing. Will tune up with AC Delco plugs, replace O2 sensors (all 4) and fram fuel filter on Monday.

don't skip the fuel pressure test ...

Finally got the money to replace the Y-pipe and muffler. No more codes, the right Cat had failed, but I had the y pipe so both were replaced. Put a Thrush muffler on, sounds great, not too loud, not soft at all. But the wife wants the quiet back, so I'll be getting an OE muffler (quiet ride) soon. Thanks for all your help.

Usually when the Catalytic converters blow, pieces will go down stream , rattle and plug your mufflers.

P0420 - Bank1
P0420 - Bank2

http://www.catalyticconverterwarehouse.com , is the place to buy OEM cats.

Finally got the money to replace the Y-pipe and muffler. No more codes, the right Cat had failed, but I had the y pipe so both were replaced. Put a Thrush muffler on, sounds great, not too loud, not soft at all. But the wife wants the quiet back, so I'll be getting an OE muffler (quiet ride) soon. Thanks for all your help.

You are welcome and thanks for posting back how it went.

If a cat has failed or gone bad there is usually a engine running problem that causes it to fail.
Sounds like the wife may want to hear the radio/music/CD over the engine noise.
Always keep a good wife happy.
Good Luck