I hit a bump the other day. car immediately started to run a little rough. recently had new converter and muffler put on (before hitting bump, ran fine). runs fine after start-up, after you drive it for about 20 minutes big loss of power and very rough idle. cat is glowing red. muffler is making a pinging/ popping sound inside. had flow checked a muffler shop and it was good. but i dont think they checked it hot and it only happens when hot. he told me right side manifold was 180 degrees above normal and showed heat discoloration. checked O2 sensors. right side was broken causing engine to run lean. replaced but problem still occurs when exhaust starts to overheat. no codes present. thoughts?

 

Did you create an exhaust leak somewhere when you hit the bump? Almost sounds like air is getting in there and when it goes into closed loop, it thinks it is lean and it starts to dump fuel.

 

Hot EGTs mean the engine is running lean, not rich (dumping fuel). Running rich would cause lower EGTs.

IMO it sounds like the cat is clogged.

 

Sounds like the cat is stopped up....have you looked under the car at the exhaust for damage ???
Maybe the bump collapsed the exhaust pipe after the New cat slowing the exhaust flow causing the cat to heat up after the exhaust is full of hot air ??

I see were you had a muffler shop check the flow....but the only thing that would cause this is a blockage in the exhaust . after you inspect it for damage if you can't find anything wrong take it to a different shop

 

in my time with cars every time my cat was glowing that meant a restriction. meaning its stopped up. can you unbolt it and drive it around see if it happens?

 

High exhaust gas temps are caused by lean conditions but overly rich conditions are what causes the cat to run red hot. The fuel is actually combusting in the cat...

The cat is now ruined. Fix the over-fueling condition and remove or replace the cat.....

 

i checked for dents when i got to my dads shop (ironically thats where i was headed). it all looked good. we had his exhaust guy check it out, he did a flow test and said everything was normal. is it possible for the cat to only be obstructed when hot? my car runs great for the first 20 miles/ minutes on my commute to/ from work. its very consistent on when it starts to hesitate and loose power. same distance all 3 times its done it. i would def try to unbolt the cat but its welded on and i just wanna explore all possibilities before cutting up my new exhaust. and....i was wrong. the o2 sensor actually had the car thinking it was lean and was dumping in fuel to try to bring it up. when we tested it the right side was sitting at 4mv. the left was in the 8 and 900s. i replaced both of them and now they are both consistently in the 8 and 900s. never drops below 800. so something has my car running rich. problem still exists after replacing them. runs great for about 20 miles of highway driving (65 to 75 mhp) then starts to hesitate and rough idle. eventually brings my car to a crawl. struggles to do 10 mph. lot of popping and pinging in the muffler. heavy gas smell.

 

his exhaust guy also said that the right side manifold (the side with the broken sensor) was showing heat discoloration and was running 180 degrees hotter than normal. but that was before we fixed the sensor.

 

Have your exhaust guy check the flow when the car gets hot ...
by driving the car a safe distance and back just enough to get the car to the point where it wants to act up. post back results ....
if your convinced that its not the cat scan it for codes .... Also you can drill two small holes in the exhaust pipe right before it goes into the cat the small holes will let the hot exhaust out. ( " it will make a hissing sound" ) after your done simply weld holes up

 

While not impossible, that was a lot more common in the late 1970s or 1980s or with the old pellet converters that used to clog up. It's also not likely that he has some condition that only clogs up when he has been driving it a while. If his honeycomb converter is destroyed, it will more likely make a rattling sound as he is drives around.

 

Reread my earlier post and see if you can understand the logic behind what I said. If false air is getting in there, it will think it's lean and that makes it run rich. If it runs really rich, it will incinerate in the converter and get all cherry red.