Hi,
I have a 1997 f150 with a 4.7L v8 and my check engine light recently came on...I had the code read at Autozone and it said it was PO401 (insufficient fuel flow)...since then i have replaced the DPFE sensor, egr valve, and cleaned all the ports and hoses. After resetting the light i drove it for a while and the check engine light came back on. I took it back to Autozone and it was still po401. What else could be causing this? Any help would be greatly appreciated! Thanks.

 

Fuel filter?

 

Use the search feature. Tons of threads on P0401.

By the way, its not insufficient fuel flow, its insufficient egr flow. Good Luck!

 

It could be a PCM problem. How bad were the ports blocked and how did the 2 hoses to the DPFE look?

 

Try this, Find the egr valve, pull the vaccum hose off, take a hose about the same size, put it on it, start the car, go back to the EGR and SUCK the hose, no literally, if the engine stalls when creating a vacuum the the ports are clean in the manifold, if no change, they are clogged, google for a thread on how to clean The intake manifold.

 

I hate to be ther bearer of bad news but this code is a pain in the a$$
Do you have an aftermarket air filter? (k&n) the oil from the filter has been known to coat the electrodes in the MAF. You will need to clean them. Pick up a can of MAF cleaner at o'riely or autozone.

1. DPFE Sensor $120 from ford. Dealer part only.
2. EGR valve
3. EGR Vacuum regulator
4. Check the line from the PCV vlave tothe back of the intake manifold. These tend to melt behind the throttle body.
5. Throttle body ports, Located under the throttle body inside the intake manifold. Takes about an hour and a half to clean them. You can find a good write up on this web site of how to do it.
6. MAF (see above)
7. O2 sensors, downstream or upstream, dont remember, just replaced them all for $275. You can do it yourself no prob.
8. Intake manifold gasket leak. Do you hear a sucking sound at idle or accelerating (like a turbo almost). Any engine racing?
9. Vacuum leak
10. Bad catalytic converter

Dont bother with the fuel filter or injectors. That's a different issue.

I have done everyting above except get my cats checked. I still have the damn light. Truck runs great though. Gets a big WTF in my book.

2000 F150 4.6L Windsor
Hypertech 93 Octane Tuning
Transmission Firmness Tuning
k&n filter

 

Is it me or is this code more predominate in the 4.6
I may be wrong but it seems like when I read about this code and people who have tried everything and still have the code, it seems like they have the 4.6.
Feel free to correct me if I am wrong. 5.4 guys chime in if you have had the code and tried everything. Curious why the code is so stubborn.
I have repaired this code on 3 focuses and 2 explorers and all needed DPFE sensors.

 

LOL, you noticed - hahaa, Yeah , the 4six is better known fouling out those sensors and plugging the EGR ports - Fouling the TB itself ..

 

When mine threw po401, it has the ports in the upper intake being plugged up with carbon. It was easily fixed by cleaning the ports. Yes, this is common to the 4.6.

 

Ok, I remember reading now how those ports tend to clog up.

Hmmmm, this could quite possibly the 101st reason why the 4.6 IS NOT superior to the 5.4 in that ..."other" thread.

 

I had those codes and took the throttle body off and cleaned the ports & the codes went away. Easy to do. About two hours. Try this link.

 

I had these codes and took the throttle body off and cleaned it. The codes went away. Easy to do about two hours. Try this link.

http://www.fordf150.net/howto/throttlebodyclean.php