yo;
Here is one fix: "...well I pulled the throttlebody off this morning ,I found that the ports to the EGR were completely stopped up! Itook the butterfly section off, dug out all the carbon and sprayed it out with carb. cleaner. The truck hasnt run this good since i bought it !..."
see this in:
http://www.superford.org/forums/posts.php?threadid=3080&postid=16595#16595
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and:
"Possible Causes of Too Little E.G.R. P0401 EGR Flow Insufficient Detected-
your EGR valve isn't letting enough exhaust into the intake system, or the flow is obstructed somewhere. Check the following:
Control input to EGR valve
EGR valve response to input (does it open?)
- plugged E.G.R. passageclean the valve
- defective E.G.R. valve. Repair: Replace valve.
- exhaust back pressure too low. Repair: Check for missing catalytic converter.
Unobstructed flow path (no carbon buildup) to and from valve
adjust idle to specs..."
source is:
http://www.autotune.com/techtips/egr.html
...
and ----
Possible causes:
Fault in vacuum supply to EGR vacuum regulator solenoid.
EGR valve stuck closed or iced.
EGR valve diaphragm leaks.
EGR valve or flow path restricted.
EGR vacuum hose off, plugged or leaks.
VPWR circuit open to EGR Vacuum Regulator solenoid.
EVR circuit to PCM open.
EVR circuit to PCM shorted to PWR.
Differential Pressure Feedback EGR (D.P.F. EGR) sensor pressure hoses both connected improperly.
D.P.F. EGR sensor pressure hoses reversed.
D.P.F. EGR sensor VREF circuit open.
Downstream pressure hose off.
Downstream pressure hose plugged.
Damaged orifice tube assembly.
Damaged EGR Vacuum Regulator solenoid.
Damaged D.P.F. EGR sensor.
Damaged PCM.
http://www.ford-trucks.com/forums/archive/topic/119770.html
to test the egr:
http://autorepair.about.com/cs/troubleshooting/l/aa042603a_10.htm
