Code 401 Egr problems
 

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.

Like sick&twysted said. Start by cleaning the EGR ports in the throttle body. If that doesn't fix it, change the DPFE.

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.

I posted a very good explanation on how to troubleshoot this a couple of days ago in the Expy/Navi forum (same engine).

See if you can locate it.

Steve

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.

Yes it's the same thing but what's weird is that their motorcraft part is way cheaper than what the dealer has.

Here are some before and after pictures of the EGR passages on the Throttle Body to Injector Spacer when I cleaned it.

https://www.ford-trucks.com/user_gal...id=183931&.jpg
What it looked like when I removed the spacer!
https://www.ford-trucks.com/user_gal...id=183932&.jpg
What it looked like after cleaning it.

I would clean the TB EGR ports first (it's free and takes bout an hour). After that, reset the code and see if it comes back. If it does, then you can spend $$$ on the DPFE.

Check this link out.

https://www.ford-trucks.com/forums/2...-egr-flow.html

What do you use to clean the ports with?