96 tbird - the exhaust saga continues

Well, I gave in and replaced the whole head pipe assembly to get rid of the P0420 and P0430 codes (catalyst efficiency below threshold on banks 1 and 2) I was getting (and the car was starting to sputter at stop
lights). Now I get a different engine code - "P0402: EGR Flow Excessive". And the car still sputters at stop lights. Have I just exchanged one set of codes and 1 KilloDollars for a different set of codes? I also notice a tapping that seems to come from under the car when the car is accelerating to higher speeds (like entering a highway). The tapping speeds up and slows down with the RPM's of the engine.
My car is a '96 Tbird with the 4.6L engine and 142k miles.
How screwed am I?
Thanks in advance for any help.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Brian Steele wrote:

Here is an analysis (not mine) of that type of engine code and what one might do about it: http://www.miata.net/garage/egr.html
It sounds to me like (a) the exhaust hangers are not stiff enough or out of position such that the pipes "tap" some other part of the car. And (b) the EGR regulator is a Moving Valve which is part of the EGR feedback system. So if the EGR valve gets extra motion from the 'tap's then the feedback system has to readjust the setting to compensate for the motion; this leads the computer to think that there is excessive flow - just a theory. - RM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
two things come to mind - I have a 4.6 and had to do both. The passages in between the manifold and the elbow to the throttle body get clogged from time to time and need cleaned out. Also, there is a sensor that watches EGR pressure and controls the valve (dpfe?). It can fail or gook up or the hose can fall off. It sits behind the throttle body next to the firewall - has an electrical connector and a hose.
You might Google newsgroups for P0402 or Ford P0402... lots of stuff about it...
PoD

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul of Dayton wrote:

Thanks to all who replied - I have an appt. with the dealer tomorrow morning (wonderful way to spend my day off). They're going to run the Dreaded Dealer Diagnostic$ and probably replace the DPFE and/or the EGR valve. From the posts I've read here and on the net, I'm convinced that I have EGR/DPFE problems, and I think I'm sufficiently braced for impact.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The EGR may be staying open, which will cause both the cat converter codes and the EGR codes. The converter codes as I said before can be caused by anything that changes the exhaust oxygen. The problem needs to be DIAGNOSED by some one competent, as you found out replacing parts based on a code can be really costly especially when the parts do not fix the problem.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well, the cat problem was diagnosed at the dealer. I didn't notice the tapping until after the head pipe assembly was replaced. I'm kinda wondering now if something could have gone wrong in the head pipe assembly replacement that could effect the EGR valve. (sensor connection got knocked off, piece of debris interfering with a sensor, etc.)
Thomas Moats wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just because it was at a dealership, does not mean the technician understands and is competent.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.