My engine light came on,so I plugged in my computer and received
a code PO401 EGR FLOW INSUFICIENT.
I have already replaced my EGR valve and that didn't take care of
the problem.
Thanks for any help.

 

Do you have the 4.6L engine?

 

EGR valves seldom go bad.

DPFE sensors and clogged EGR passages are th two most common faults.

SEARCH keywords "P0401 EGR vacuum test"

Steve

 

you could also check to see if any egr tubes or lines have a crack in them.

 

probably a DPFE, check your DPFE voltage should be between .2-1.3 volts with key on engine off and at idle. If its higher replace the DPFE, if you have a vacuum pump apply vacuum to EGR valve with the engine running and if the engine sounds like it is going to stall or does stall then your EGR passages should be ok. If you apply vacuum and the engine idle is not effected or has very little change then check the EGR passages and hoses for clogs.

 

The EGR seldom goes bad. Most of the time P0401 is caused by a faulty DPFE and/or clogged EGR ports. Takes less than an hour to clean out the ports and change the DPFE.

 

I have a 99 4x4 with a 4.6. My CEL came on so I checked the code and it was a PO401. SO I decided to change the EGR and the DPFE. 2 weeks later and the code has returned tonite. humm guess I need to do some more checking.

Mike

 

Yeah, sometimes the ports on the 4.6L throttle body get a bit clogged and cause an insufficient flow...

 

YES, 1997 4.6L 4X4

 

Thanks For All The Suggestions.
One More Question Is How Do I Clean The
Egr Passages And Ports?
Do I Use A Type Of Carb Cleaner And Spray
Into The Passages Or Do You Recommend
Another Type Of Cleaner?
BY THE WAY MY TRUCK IS A 1997 F150 4.6L 4x4
THANK YOU

 

There is a two-page procedure here to clean the throttle body if you think your mechanically inclined enough. You can also clean the IAC while your at it.

http://www.fordf150.net/howto/throttlebodyclean.php