ok took my truck to get inspected today and it failed, failed bc it threw a cel p0420, catalyst efficiency below threshold, and it was releasing too much visible smoke, i know that the code means that my catalytic converter is bad, but would a new catalytic converter reduce the amount of smoke that the truck is releasing, i cannot find anything else and would appreciate an answer thanks in advance for any answers or help.

 

Does the smoke have an odor to it, like oil? Your old cat might just be caked with deposits and they are burning off as it heats up. Does it smoke upon startup when it is cold?

 

Sounds like your cat is clogged/old. A cat is designed to burn anything left over at the exhaust level, most importantly Hydrofleurocarbons. When a cat is dead this **** passes through to the muffler and finally our atmosphere. if you are seeing black exhaust and have no other issues, replace it, pass and save our planet.

 

yes it smokes when it is first turned on, but no more than any other car(and it usually stops once the car warms up)and it smokes the same color as it did while we were at the inspection station, and that was after about 30 miles on the highway, and with the check engine code we have to replace the catalytic converter anyway so if it is just the deposits burning off after 195000 miles on it and i replaced it and the problemsstopped i would be happy any other ideas would be appreciated, unless there arent any, then i can do this with confidence and there is a smell to it, and its really bad, not sure if its burnt oil smell or not

 

well the smoke is white like when you start a car cold, and yea i intended on replacing it, thats not the problem, i wanted to know if replacing the cat would also fix the visible smoke problem and it sounds like it will, so thanks

 

Depends. Run a compression test to be sure that is not a problem. With 195K miles may need to have some valve work.

 

pistion rings have to be going...blow by, valves...do as jk240sx said so you can see where to start

 

just want to get it through inspection w/o any major work then im probably going to dump it at this point

 

dump it now not worth it most likley if shez smokin wiht that many miles...

 

we are going to as soon as its inspected bc no one will buy a car around here that has a failed registration sticker in the window, but as soon as we get it passed we are getting rid of it