any one know how to tell if a catalitic converter is stopped up im thinking mine is my car will drive fine then like it will die off and lose power and bog down so ill trhow it in neutral and rev it up to like 4k and throw it back in drive and it will go back to acting normal any ideas on what my problem may be my car is a 350 tpi carte engine automatic slapped in a 86 iroc z

 

Put your hand over the exhaust. If it's blowing good then the cat isn't blocked. If it was blocked to any great extent the engine would run bad all the time.

 

I agree that the engine would run bad all the time if the cat was blocked too much, but just as much exhaust should come out if the cat is partially blocked or not blocked at all.

 

sometimes car will run fine at cold with clogged converter, as gases has not warmed up enough to expand, easy way to find out if clogged if thers a o2 sensor in front of converter take it out and run down road, if no o2 sensor in front losen pipe going into manifold and drive down road if runs better you know converter is clogged

 

if your cat is blocked your car will run really hot like really really hot , I had the cats clog on my 94z28 and it wouldn't go over 20mph and the motor got smoking hot.

 

Just took a bad cat off of my 89 L98. It had dual cats, and just 1 bad cat made performance drop what felt like 75 -100 horses. The exhaust note changed as well. It sounded like there was a dead cylinder or two. Felt like it as well.

The car seemed to idle ok.

Also, I could hear the innerds rattling around when I hit a bump or rapped on the case of the cat.

When I took it off of the car, the rear half of the material inside was broken off and plugging the outlet pipe.

 

If its badly plugged, it will get VERY hot... like litterally glowing.