Dodge Ram runs like a dog

taking truck to get CAT replaced today,was thinking temp was good but it is 490 on intake end and 360 coming out,thats wrong,i was mistaken and what ive read is it needs to be hotter coming out then in. sheeesh this is getting old and the sensors i have not pulled them priced them to replace last night and figured i will wait, they arent cheap but by the truck getting worse i will get cat replaced and go from there. thats not it then back to the drawing board  

Actually CAT need to be hotter than 490 to work right and some cooling across it is normal because as exhaust expands over it it cools. Sounds like you have a low restriction muffler behind it based on temps. Also if it was plugged, temps would be a lot hotter.  

no those o2 sensors aren't exactly free but if ya neglect them they can only lead to more problems later (or now) try pullin' 'em out 1 at a time and at least eyeballin 'em and see if one looks obviously bad. ya got one after the cat, one just before, and possibly one on eash side just below the exhaust manifolds. try the bottom ones first. but i still think the meatball of it all is that durned intake gasket. i would follow snomans advice on the long hose to the cab to get a good accurate test. don't give up on yer ole mopar yet, once ya get this ironed out youll remember why ya love her. this is still cheaper than payments on a new one right?  

The ones after CAT play no roll in mixture control.  

Ok took CAT off and threw it down, plugged, was my first thought but anyhow the truck runs great now, better then it did b4 it instantly dropped. sensors appear fine from just lookin at them.the distributer cap looked bad and i am sure the plugs and wires helped. I appreciate all you guys help on this dang thing,least tomorrow when i drive to work i can leave at normal time,stead of an hr early,lol Thanks  

It is surprising that temps were not hotter with plugged CAT. Exhaust cools as it expands and high back pressure would tend to keep temps higher.  

well those temps were at about 10 minutes of idle.the cat probably would be higher then what i read at that time, i know its like a new truck tho now.  

glad to hear it! now go beat on it like a red headed stepchild.  

if it will help my 96 5.9 did the same thing   but i finally figured it out  what i found out was the fuel rail was dirty    you see the only fuel filter is in the tank  and there is no return line for anytrash that gets through the filter so what i did was put inline fuel filter on it under neath the drivers floor board i mounted one  i cleaned out the fuel rail with carb cleaner sprayed the injectors down real good  put it back together and it was like a new truck again  the whole process took about 2 hours      hope it well help you and good look with it