I have a '97 4.2l...around 6 weeks ago my check engine light (CEL) came on. I took it to have the code read at a parts store. It read 0401 or 0409 I can't remember but it meant EGR was insufficiant. I have since replaced in order DPFE, EGR, EGR Solenoid. I have reset the codes each time and each time the same read comes back. Then I took apart the Throttlebody, IAC and cleaned them. I have also taken the new parts off and put them back on to make sure I didn't make a mistake. I need advice desperatly.

 

Here's some links I found using the search function. I'm not sure about your paeticular engine, but your egr ports in the intake elbow may be plugged with carbon. Good luck.

https://www.f150online.com/forums/sh...ight=egr+ports

https://www.f150online.com/forums/sh...ight=egr+ports

 

I have changed the pcv and both rubber ends, all o2 sensors. The codes are going between P0401 and P0402. P0402 is EGR excessive flow and P0401 is EGR Insuffecient Flow, I think. I am at a real loss here. Any suggestions.

 

Just experienced the same issue with my daughters 2000 Ranger 2.5 .
Found that the EGR tube had actually rusted through at the bottom end where it connects to the exhaust manifold. Check your tube for cracks and make sure the lower connection is tight....