99 3.8 139,000. new engine at 118,000 and new egr. The car will barely move under load, idles fine. getting some rattling from underneath by the catyletic converter. I am thinking bad converter causing all other codes. what do you think?

 

The main problem seems to be the EGR as the PCM does not see the EGR pintle moving as commanded. The misfire code is most likely related to the EGR. HOWEVER, if the cat , as you mentioned, is messed up and choking the engine it will cause all of the problems. The engine will misfire, and the EGR may be moving as commanded but the excessive back pressure will force exaust gas back through the EGR and into the intake causing the EGR codes to be set, not to mention that excessive back pressure will cause severe power loss. You can have the cat tested for excessive back pressure to make sure. If you do change the cat, it would be a good idea to clean out all the carbon from the EGR and associated passages, and put in new set of plugs.

 

But...but...but...I thought backpressure was good?
Bang on the cat converter and listen for a chunks of rocks sound. Could be broken up inside, but it sounds like you need to give the cat a close look from the inside regardless.

 

Now we know what back pressure is good for. Back in the very old high school days, we used to stuff a raw potato into a teacher's car exhaust pipe, and laugh our ***** off as he tried to drive out of the parking lot.

 

Yeah, my dad told me about that trick many years ago.
I'm not implying anything...just saying. lol