misfire p3000 after catalytic converter replace

[Magnacharged H2]

I just replaced a clogged catalytic converter drivers side on my 2003 H2. Now I,m getting a misfire code.
Truck runs good once underway , but at idle it runs rough, rpms drop and coolant temps start to rise.
I,m thinking it is vacuum related. Anyone else have this problem after replacing a cat ?

[HUMTECH]

You only replaced one side? Are the o2 sensors working properly? Sure the muffler is not restricted? If the cat was welded in did they get a good seal at the weld points? Too many variables to diagnose without more info. Try to get a scan tool on it that can monitor misfire counts and find out which cylinders are misfiring. Check your o2 data make sure you dont have a dead or lazy pre cat sensor. Doubt you have a vacuum leak as that would increase idle speed and set a lean code.

[HUMTECH]

Oh and im assuming you have it supercharged. Was the repair done at a dealer? Maybe they reprogrammed your pcm thinking the updates would help and wiped out you ecm tune for the charger...

[Magnacharged H2]

Thanks for the reply Humtech!
The scanner I have reads random misfire right bank , but not which cylinder it is.
I replaced the drivers side cat with a Magnaflow universal cat. I welded in myself.
No dealer flash on ECM .
I, ll see if I can get someone with a better tech tool to check o2 sensors
Thanks

[HUMTECH]

If your misfiring on the right side ill bet that cat is plugged as well. Anything over 0.5psi backpressure can cause misfires on that bank

[IRA51]

Over the years I have found that it's best to replace both cats and all 4 O2 sensors at the same time . Did you weld the cats in while they were on the vehicle with the battery conected ? If so ,your lucky you didn't fry the computer.