P0401 Codes, nothing left to replace. HELP

[xtinc7ion]

Ok so I got my expedition more than a year ago. Ran great for about 9 months then started hesitating a LOT and idle was just ****** most of the time. I went and had it scanned and found the P0401 code was popping up. This is a list of what I have done to fix this...

1. Cat delete I know this causes an issue with O2 sensors but I can worry about that later.
2. EGR Valve replaced
3. EGR Vacuum Solenoid replaced
3+. Missed one, Idle Air Control Valve replaced
4. DPFE sensor replaced
5. PCV tube and Valve replaced
6. Throttle body and EGR flow areas removed, and cleaned out
7. MAFSensor replaced
8. New CAI installed (not that this has anything to do with EGR, but wanted to eliminate any kind of intake issue as well)

I had the truck running pretty much great for a month or two, and now its back. Cold start ups drive like its choking till I give it a good rev or two, then its back to ****** idle and some intermittent hesitation from stops. I am not sure if my P0401 code is gone, I will check again tonight. I do have the code from my O2 Sensors up so its hard to tell when something else pops up.

I haven't checked fuel pressure yet, I will do that asap. I was thinking the idle issue may be a misfire, so I thought about changing plugs, wires, and my two coil packs(I do not have COP) but I wanted to wait to see what you guys thought before throwing money at it.

Any ideas would be awesome, thanks!

 

[1997SCEBFEX]

Iac?

 

[xtinc7ion]

Iac?

haha one I forgot to add to the list! Yes I replaced the Idle Air Control Valve, it was like the third thing I replaced. Thank you for your help though. Would have been a great piece of advice!

 

[96mustangV6]

Have u check all the lines. I had a idle problem in my navi. Sounded like it had a huge cam in it. There us a 90° elbow one the very back of the intake. You can't see it but can fill it. Its connected to the pcv valve. The rubber on mine was rotted out. Oriellys sells the same elbow cause one opening is bigger than the other. Mine threw a code to. But can't remember what code it was. May be worth a shot. I had 2 lines from my pcv valve that were cracked and had holes in them.

I think it threw same code as yours. Now after I replaced those lines it idles perfect and no light.

 

[xtinc7ion]

Yeah I replaced that whole thing, used some fuel line for it to get rid of all the breakable things in the line. I am wondering if the new one failed so I may check it out again. Yeah mine sounds like it has a huge RV cam in it lol finally someone else sees it the same way.

 

[96mustangV6]

Yea mine went from 500-900 lol. Sounded meaner than my dirt car. Lol

Did u check the elbow on the veeeeeery back of intake though. Like I said you can't see it. You have to feel for it. The opening on intake us bigger than the opening on the line. It was a pita to replace being as its like 2 inches from fire wall.

As soon as I replaced it. Truck went back to normal.

Got annoying while trying to haul my car trailer every weekend.

 

[xtinc7ion]

Gonna check it now, I replaced that whole line, including the elbow, but its very safew to say that it might have melted through again, or broken. Ill post and let you know, thanks for your help!

 

[xtinc7ion]

Just checked, the line is still on there and doesn't seem to have any breaking or issues.

I don't know what it is. I really just need someone to tell me what is wrong so i can fix it!!! lol

 

[96mustangV6]

Those were my ideas lol. Have u taken apart and cleaned the throttle body. Clear the codes and see if it comes back up.

 

[96mustangV6]

Never mind I re read our first post. I'm not real sure. Sounds like a vacuum leak to me though. Check make sure intake is tight after maf

 

[stamp11127]

Check out this video, he knows what he is talking about:

P0401 EGR Insufficient flow test - YouTube

 

[FordandPolaris]

I have a similar rough idle, and I am blaming it on plugs. I have 5 original plugs with 218k on them and so when I finally get those out I will see if that makes a difference. I do not have the EGR code though. If you have not cleared the codes since replacing those pieces, I would do so and see if it still comes back.

 

[xtinc7ion]

Ill be clearing the codes here ASAP so I can see if I'm throwing one. If its something like plugs or wires I, I plan on updating those here soon anyway so that would be helpful.


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[FordandPolaris]

Ill be clearing the codes here ASAP so I can see if I'm throwing one. If its something like plugs or wires I, I plan on updating those here soon anyway so that would be helpful.


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To save time, just unplug the battery and then turn the key as if you were starting it. Then hook the battery back up and let it idle for about 5 minutes to relearn its conditions. Drive it for a couple of days and then check the codes at that point. That way you only make one stop to have the codes read.

 

[xtinc7ion]

Good call. Ill do that first thing tomorrow. Thanks!


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[mykeey]

The passage ways in the throttle body are plugged. Mine showed same code. I replaced the dpfe 2x. Took to the dealer and they said the passages were plugged. Took apart and cleaned and the code went away

 

[xtinc7ion]

See I've done that already. No way it could have re clogged again in just a couple months is there?


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[bicsintegra]

I had similar problems with my 2000 expy and I replaced the Cops, air filter, spark plugs, fuel injectors, battery, and nothing worked. in the end after about 1 1/2 years it was the alternator, now no problems with her. good luck with diagnosing I know it can be a pain the *ss.

 

[xtinc7ion]

Wow really? Lol I love how I can be literally ANYTHING haha. Glad you figured it out. If it was just my alternator I would be happy. Maybe I should get that tested.

Thanks for all the input. I appreciate the help!


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[Sonofadocker]

P0401 code

my 1997 ran fine and then I popped a rust hole in the cats.
1600.00 repair. I had rough idle in drive /stopped and high speed 75mph + detonation in the intact manifold - loud pop and truck would shake.
In twenty miles of driving P401 and P1131 popped up. Changed both upstream O2 sensors, DPFE , cleaned MAF ( very dirty), removed throttle body and cleaned it . Not clogged but blackened.

Cleared my codes with snap on mt2500 (150.00 used) and test drove. Ran so smooth and strong until high speed . Light came on and .... 401 & 1131.

When it cools off I pulling out the battery and looking at the vacuum lines by the battery . My AC Heat is on default mode defrost and floor - should be the same vacuum leak that will fix it all ?

Post back later