So here's the Story so far.....

1997 Ford F-150 XLT Supercab 4WD
4.6 W
R470W Auto Trans
192,500 Miles.

I keep getting a P0401 Code "Insufficient EGR Flow"

Here's what I've done to try to solve the problem.

1. Replaced DPFE
2. Replaced EGR regulator
3. Pulled and checked the stainless tube from header to EGR valve
4. Pulled EGR valve and checked for operation with vacuum pump
5. Pulled vacuum on EGR valve when running, reduced idle speed and "stumbled".
6. Pulled vacuum container from behind battery box and it tests airtight.
7. Pulled the big connector off the PCM and sprayed the contacts with contact cleaner.
8. Checked the integrity of all involved vacuum hoses.
9. Made sure the Throttle body ports were clear.

Today, I put a vacuum gage inline with the EGR valve to watch it while driving. Also, I put a voltmeter on the Brown/Pink Stripe wire to the EGR regulator to watch while driving.

Here's what I saw. (assume the truck is at operating temperature)

1. When the truck is started, the voltage goes to line voltage ~~13.4 volts.
2. When the throttle is depressed, IF the voltage drops, the vacuum goes up (and I assume the EGR valve opens).
3. When coming to a stop or the throttle is fully released as in coming to a stop, the voltage goes to max, and the vacuum goes to Zero.
On most test drives today (probably 10) at least once or twice it just stops responding to the throttle. Stopping the truck, turning it off and restarting seems to clear the problem for a few miles.
I really need to get this fixed as I have to get it emission tested next week for my new tag.

Thanks for any help anyone here can offer.

 

Monitor the output voltage of the DPFE sensor while pulling a vauum on the EGR valve.

Everything else you described looks perfectly normal.

If needed, connect your vacuum guage inline (tee) with each of the DPFE sample lines. Pull a vacuum on the EGR valve and monitor the vacuum guage. One of the lines will show no change (reference) while the other line will show a vacuum that is proportional to the amount of EGR flow. Track the DPFE sensor output and you should be able to see a direct correlation between the sample vacuum and the DPFE sensor output.

Steve