97 Expedition OBD II code P0401 (CEL on)

My 97 Ford Expedtion check engine light is on and is giving a diagnostic code P0401 (EGR flow insufficient). I have replaced the EGR soleniod, DFPE sensor and Oxygen sensors. I had a mechanic check the EGR valve and he said it wasn't block because it was opening and closing. Anyway after reseting the code within 30 minutes of driving the CEL comes back on for the same problem. Could it be that the EGR valve is really bad? Could there be a blockage somewhere else? Does anyone have any suggestions?

The egr ports under the throttle body carbon and plug - to test for this start the ingin and removed the cover to the EVR (egr valve regulator) and plug the hole in the top - check for vac. at the hose to the egr valve - if there is vac. then you most likely have plugged ports - remove the throttle body and clean out the egr ports (normaly with a small punch and some carb cleaner

I am searching to find a fix for the same problem on a 98 expedition. I have replaced the DPFE (twice), EVR, and EGR valve. I have cleaned the throttle body passages, they are spotless now but they were completely clogged. I have taken off the tube from the exhaust manifold to the EGR valve twice and cleaned it with carb. cleaner and compressed air. I am still getting the Check Engine light and P0401 on the scan tool (supposedly Insufficient EGR Flow). Gas milage is bad as well.

Can anyone help me determine what this problem is?

check vac. to evr - if you have full manifold vac at valve - remove the cap off of the top of valve - put a vac. gage on the egr valve hose and plug the small tube sticking out of the top of the evr and make sure you have full vac. to egr valve - 97-00
exp. and f-150 have problems with the vac. lines getting brittle and breaking due to heat and the rubber fitting on them rotting away

Thanks, I am going to check it the next chance I get. By doing a little more research on this problem after I posted here last time, I found others have had a vacuum problem as well. I hope it's that simple.

I removed the wire loom from the vacuum lines and pulled the battery to have a better view between the battery box and firewall. To make a long story short, all three vacuum lines were rotted through/apart where a previous battery had leaked on them. Ford wants $140 for the new vacuum line assembly and I won't pay that. So I put some rubber line in place of the rotted part and I haven't had the CEL come on. I have driven it about 30 miles. The light usually comes on around 10 minutes of driving after having the battery disconnected. So far, this seems to be the fix. The only problem is now I have an extra EVR and DPFE sensor.

Thanks for the help.

My check engine light stays on and then when I start driving steady it flashes. What is the problem

the only reason for a flashing mil is a detrimental
missfire - if it is a 4.6 you probably have bad plug wire or a 5.4 on of the coils is bad - look at coil on cyl. 4 (pass. side rear) there is a heater hose above it that likes to drip on the coil and kill it - if the hose is leaking it should be obvious just by looking at the coil - it will have crap built up on the top of it compared to the others - these are the best places to start - if they aren't obvious the unplugg the injectors on at a time untill you find the cyl. that is missing and go through and test the crap on that cyl.

I have replaced every o2 sensor at least 3 times....make sure you have replaced the right ones...there should be 4.

If you drive alot, and it gets HOT where you live...the PCV valve may be collapsing, and causing a vaccum problem. I am on my 4th PCV valve assy....Buy the Ford ones. I live in the south, drive 50-90k miles a year, and replace mine at least once a year!

Good Luck