I'm getting this P0401 code intermittantly.

I have 101K miles on my 1998 F-150 supercab 5-speed, original owner. Other than regularly changing oil/filter every 3000, all I've done to the engine is change plugs and wires at 60K, and air filter every 15000.

I guess I need to clean out the EGR area. Where is the EGR area located? What should I look for, and what should I clean out?

Also getting bad gas mileage, about 12MPG, used to get 20MPG back in a day. (I just changed air filter with a new fram.) And there is an unburned gas smell in the exhaust, more so when it is first started and warming up. Could this be related to the EGR code issue?

Anything else I could/should do to it at this point?

Thanks,

Jon

 

hi, look in the passenger side engine bay and see if you can see a spaceship shaped steel thing with a black rubber elbow vacuum pipe. thats the egr valve.
there is a half inch dia steel pipe coming from the exhaust manifold and that is all part of the egr system.
sorry i cannot help with any problems as i simply blanked off and removed the whole system due to the pipe rusting-out and no replacement available in the uk but i am sure a search with fetch-up all you answers. good luck bokker.

 

Cheers, Bokker!

I see the EGR stuff exactly as you say. Now I just need to figure out what parts and how to disassemble and clean them up, I guess.

Hey--I had my 1998 F-150 over in the UK in Cambridgeshire when we were stationed with the USAF at RAF Alconbury from 1999 to 2002. Absolutely loved that assignment. The big American pickup got lots of looks driving it all over Brittain and Ireland. That was fun!

Jon

 

hi, nice one, thanks for that. head turning in the uk is a guarantee but try getting parked !
pleased you enjoyed your stay. bokker.

 

OK. So after reading a lot of posts on the dreaded P0401 code, here is what I did:

I pulled a vacuum on the EGR valve running at idle. (Ahem. Actually, I, uh, sucked on a plastic fish tank line!)

The engine immediately stumbled and fell during this test. (Actually, it nearly died once because I sucked too hard. No hom_o.)

So, I opine that the result of my "vacuum" test means that my EGR valve is in fact working just fine, opening and closing as it should, AND (yay!) that my EGR ports are not all completely stopped up with carbon and that they will actually let exhaust gases into the intake, no problem. (Whew!)

Now, I started to narrow in on the DPFE sensor as the potential culprit. I could have broken out the old digital volt-meter to do the voltage test on the DPFE and see if it is giving the 0.8v to 1v at KIEO and at idle. But...Nah! That would take too long. Instead, thinking that it must be the DPFE, I remove it and, eew, would ya look at the goop inside those tubes?! Definitely shot.

Now I'm pretty sure it's gotta be the DPFE sensor. I wonder if I can clean that thing out and get it working again? Nah! I'd probably break it.

So off I go to the A.Zone and pick up one of their $52, much maligned "cheapo" , DPFE sensors. (Hey--the "quality" Ford DPFEs are now made of plastic, too. Imagine that!)

2 Minutes after getting it home, I've swapped out the DPFE's--how easy is that?! And, hey is it just me or does the idle sound better and a bit stronger?

So, I clear out the codes, and next morning I drive 25 miles to work. Hey, how about that--the gas mileage has picked back up!? Great!

The computer finishes running its tests as I pull into the parking lot at work, and (YAY!) I get a green light on the Diagnostics--No codes in the system!

100 Miles since then, still no CEL, no code, and the gas mileage is back to about 20+MPG, just like back in the day!

Question is, do you think I fixed it by changing the DPFE sensor, AND should I mess with anything else at this point, like an intake cleaning?? Or is that tempting fate on this 102K engine?

At any rate, I've never touched the MAF sensor. Do you think it is worth cleaning that thing at this point? I get no hesitation from the engine, a smooth reliable idle, and plenty of power.

Thanks,

Jon

 

"still no CEL, no code, and the gas mileage is back to about 20+MPG"
hi, to my mind you have cracked-it and i would leave well alone.
nice one, bokker.

 

I'm late getting to reply, but I'd agree with bokker.
Appears you have the problem solved. And as my signature says......

If it ain't broke, don't fix it.

Glad you got it squared away with relative ease.

 

Thanks, Bokker and Brian,

So now I cleaned my MAF with some CRC-brand MAF spray cleaner. Why not? I'm on a roll after that EGR stuff!

I fire it up and immediately I get a P0113 code, air flow too high.

What gives? Did I clean it TOO good? Did I break the MAF sensor?

Guess I should taken your advice, Brian, and left it alone?

 

hi, the code may go away when the ecu has reset it self to its new clean setting. run it for a while and see. bokker.

 

If it does not reset after driving a little, I'd open the intake plenum back up and look closely at the MAF sensor. As you probably know, the MAF sensor is a very fine wire that stands in the air intake stream. It is heated when the engine is running. Air moving across the hot wire cools the wire.
The data provided through monitoring current flow through the hot wire (current will vary with temp) is used in conjunction with other sensor input to provide air flow data to the ECU.

I'd look at it real good with a flashlight to see if maybe the wire is broken.
Also, check surrounding wires and connections. A problem with another sensor might show up as a air flow high fault due to invalid data input to the ECM.

I have never tried it, but have been told you can unplug the MAF sensor and the ECU will revert to generic MAF parameters. You might try that to see if the code clears.

Worst case, buy a new MAF sensor.