Can a clogged EGR Port cause falls emissions code issues (ie: O2 sensors, CAT, EGR Valve), and cause rough idle?

 

A clogged or inoperable EGR will cause high NOx, and a lean misfire through part throttle, which would cause a spike of all emissions output. EGR is not active during idle so it would normally not cause an idle issue unless a chunk of carbon has blocked the EGR valve open, which then would cause a rough idle.

If you have codes, post them up.
If you have had a recent emissions test, post up all the numbers.

 

Thanks Mad_Mike
I have a sneaky feeling that the carbon buildup is the main issue. Hopefully once the EGR and port are restored the codes will go away.
DTC's: P0401, P0420, P0452, and P1491

 

P0401 is insufficent EGR flow
P0420 is catalyst below threshold(this will happen if EGR has failed)
P0452 I believe is EVAP, related.
P1491 is related to the EGR solenoid.

IIRC in the ACCORD FAQ at the top of the page there is a link to a thread regarding a warranty issue with EGR function on the J30 Accords. But I have no idea if Honda will now warranty that after 11 years. Eric the carguy on YT has a video on how to clean the EGR on the V6s as well.