Took my poorly running 99 max to the mechanic who replaced EGR valve. Most of the symptoms seemed to have been taken care. p0400 and p0500 codes come back. Runs fine for the most part but starts hesitating during acceleration occasionally. Only seem to experience it after car is warmed up which makes me think it is probably related EGR system still. What else could be going on? I saw another thread about someone who had the same problem and the issues was a sticking EGRC BPT valve. They said they didn't get a code for this valve but the issue was mechanical and not electric. Could this be happening to my car? Are there any other things that could causing this?

I really don't know much about this stuff. Just wanted to see if what information I could get. Is the system the same for all 4th gen maximas? From what I read it seems like older valves rely on vacuum whereas newer ones are electrically regulated.

 

Notwithstanding the replacement of the valve itself, did your repair guy inspect and clean or replace the guide tube?

Regardless of the newness of an EGR valve, if it can't breath it's gonna be mad.