I have a 97 Z28, 6 spd, factory cam, 1.65 rockers, K&N fipk, MSD, tb coolant bypass, flowmaster post-cat exhuast, jbl headers. The SES light is not lit, however, when I take it to an emissions station (CA), the test machine indicates that the pcm is throwing a P0400 (EGR flow malfunction) code. I had a Chevy dealer work on it but they were unable to resolve the issue. After replacing a malfunctioning oxygen sensor that was causing another code they cleaned out the egr path (twice) and replaced the egr valve (twice) but the error code just kept popping back up. In addition to failing for the P0400 code it was also failing for excessive NOx emissions. They ended up just pointing to the headers and blaming "aftermarket exhaust components." Although I have not verified it myself yet, they said that there was almost no exhaust flow coming out of the egr/header tube. I know other people run these headers with no issue (and the headers are CARB EO), but I don't have the knowledge to point a tech to anything else.

I saw in another thread a member named dwayneZ28 had a similar egr issue and traced it to a "header issue." Unfortunately the post didnt contain more detail or a contact point. Anybody out there have a similar issue? How did you resolve it?

 

Headers lower the back pressure enough that the EGR doesn't function properly. You may have to have the EGR tuned out. Search on P0400 and you'll probably find more info than you want.

 

Moparman is correct. The only fix w/ headers is to have the EGR code programmed out.

WD