03 Impala LS 3800 V6 - Excessive Oil Consumption

[fishr81]

Got a problem with my 03 Impala (108K miles) where it consumes about 1 qt of oil every 2k miles. Oil is not leaking. I do not see excessive exhaust smoke either. The car has been using oil for awhile now (since 60k). During the course of this oil consumption problem, I have witnessed several other problems which I think might be related. They are as follows:
1.) Last year the catalytic converter got plugged up and the car had no guts at all when accelerating. Engine RPM's couldn't get up and tranny wasn't shifting properly. I replaced the catalytic converter and it seemed to solve the performance problem.
2.) Next, I noticed oil seeping out from around the valve covers gaskets and pooling on top of the engine. I found that the PCV valve was full of oil and replaced it. Since this I have not seen oil leakage around the valve covers any more.
3.) Next, I noticed that the check engine light came on at about 100k intermittently and now stays on all the time. I checked the codes and it said that my emissions efficiency was below the threshold. I don't recall the actual code number at the moment, but this code popped up intermittently before the last time when my catalytic converter got plugged so I am concerned that I am going to have a repeat of past problems.

My question is if anyone knows what it causing the oil consumption problem? I would like to solve it! Is it the exhaust valve stem seals? Does anyone know if there is a GM service bulletin on this type of a problem? I don't know where to look up GM service bulletins...

[maxwedge]

Oil consumption can be valve seals, oil control rings, leaks of course, wrong pcv, on several 3800's I have found the lower intake manifold inner corner bolts loose and not sealed allowing oil to migrate into the lower intake. Cat efficiency is usually caused by a bad cat, I believe these cars had issue with that and there was an extended warranty for this.

[troy1]

My Impala has the same oil consumption problem never looked into it much. I have had the car sense 28K used now it has 85K.