I have a 98 1500 5.2 with a 5spd tranny and about 199000 KMs on it. Last few weeks its been lacking power in the top end so i figured the cat was on its way out. Then today pulling onto a highway it wouldnt go over 3500 rpm. So what i did was kept my foot to the floor, heard some clunking come from behind me somewhere and all of a sudden had all my power back and more. She pulls nice and hard all the way to the redline now. Im wondering if maybe the cat collapsed and spit it out the tailpipe?

 

welcome to DF.

wow, I think you need to put a temp guage (gun) on the input and output of the cat to see what it's doing. normal cat operation is the output temp is hotter than the input. if the input is hotter than it's plugged. if they are the same, then it isnt doing anything. check it out.

 

not throwing any codes?

 

well went and had a look and temps are give or take 50 degrees hotter coming out. not giving any codes either

 

sounds like the cat is good and performing well. I've seen a 10 deg diff on the output and it still passed smog.

did it have the problem in all gears? maybe (since you heard clunking) it was in the rear end...?

 

Did the exhaust tone change and volume get louder after hearing the clunking sounds?