My check engine light came one so I had it scanned and came up with #401 which is insufficient air flow. I pulled the valve off and it appears it has been replaced before. It was not all carboned up, the vacuum pulled the valve fine and it sealed liquid tight when closed. What else could set this code? Could it be the DPFE? How can that be tested? Any thoughts. Thanks.
do a seach youll find tons of info on it. in a nutshell the first thing you need to do is clean out or egr ports in the throttle body neck. its the most likely prob since your millage is over 50k. second most likely thing is the egr pressure sensor on the egr tube. very common for these to fail but you need to replace it with the updated Ford part in a plastic case not an aftermarket one. Hardly ever is the egr the cause for this code, but you can check it by applying vacc to it while the motor is running. this should make the motor stall or close to it.
Carbon build up on the passages from the EGR valve in the Intake to Throttle Body spacer could be your problem. I bought a 1999 F-150 a month ago and it had 180,000 miles on it. When I removed the spacer and I looked inside I found so much carbon build up that it looked like leaves growing from the passages. The cost of a couple of gaskets and some throttle body cleaner may be all you need. I took some pictures and will see if I can get them online when I get home.
Thanks for the tips. I looked on Rock Auto and found the "EGR Pressure Feedback sensor". Is this the same as the DPFE? I see it right in front of the EGR valve. Is there no way to test this? I did check the going to it and they are OK. Thanks.