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.
Here is an analysis (not mine) of that type of engine code and
what one might do about it:
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
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
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.
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.
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:
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