02' 4.6l P0420 code

[20EddieBauer02]

Been getting a P0420 code, bank 1 catalyst below threshold, the engine runs great, and there is less than 1000 miles on the new o2 sensors I replaced that were not bad to start with when I was having a misfire issue due to a cracked intake leaking coolant into the #5 coil pack.
Any ideas?

 

[alexb2000]

Been getting a P0420 code, bank 1 catalyst below threshold, the engine runs great, and there is less than 1000 miles on the new o2 sensors I replaced that were not bad to start with when I was having a misfire issue due to a cracked intake leaking coolant into the #5 coil pack.
Any ideas?

I went through this exact set of problems. The coolant that leaked into the cylinders poisoned the catalytic converters. Now you need new ones. I paid about $500 to have two good quality ones put on and haven't had another problem in two years.

 

[20EddieBauer02]

There was no coolant that leaked directly into the cylinders that I know of. The car its now lacking power but has what seems to be plenty of flow out of the exhaust.
Also I'm having trouble finding converters.

 

[alexb2000]

There was no coolant that leaked directly into the cylinders that I know of. The car its now lacking power but has what seems to be plenty of flow out of the exhaust.
Also I'm having trouble finding converters.

If you had coolant leaking into the coil pack that usually means it goes down through the plug and into the cylinders, then out the exhaust. This usually happens slowly and often you get a coil pack code at one time or another. Then later you get an O2 sensor out of range code. Both are caused by coolant from a leaking intake. If you search there are many here that have had the same problem.

 

[20EddieBauer02]

Well that sounds right, I'm guessing it's not a good idea to drive it until the converters are replaced?
Also where is the best place to get the converters?
Oh and the car runs great but does not want to downshift when flooring it.

Edit: Found some on rockauto, are they worth getting?

 

[alexb2000]

Well that sounds right, I'm guessing it's not a good idea to drive it until the converters are replaced?
Also where is the best place to get the converters?
Oh and the car runs great but does not want to downshift when flooring it.

Edit: Found some on rockauto, are they worth getting?

Rockauto has some good products, they also sell the complete exhaust.

I would try not to drive it until they are replaced.

I did it a couple of years ago and no problems since.

 

[20EddieBauer02]

Not sure if I need to but, I did order the 450 dollar Ypipe assy. shortly after this thread. Cut the 3rd cat off, wow, don't ever wait around when they plug up. I never drive it so I let it go, hard to tell how much life I took out of the engine.