P0401 CEL...Truck runs bad now

[atvkid4eva]

hey guys for the past couple days i have had a CEL engine light on my 97' 4.0..it would come on and off for a couple days and recently it is stuck on..had the code ran and is it the P0401 whcih i know is EGR insufficient flow...and ive read and read on here about the dpfe sensor and that it usually isnt a faulty egr valve...well my question is that my truck is starting to run crappy since this CEL has come on...the other day it almost stalled while idleing at a stop light and when driving home on the freeway it seems like it wasnt getting gas and almost stalled? are there any noticable symptoms of this CEL code? let me know what u guys think i should do thanks. -Bobby

 

[atvkid4eva]

well today at a stop light while i had the brake on sitting there in drive waiting for the light to change the rpm went from about 700 to 1100 and the truck died...started right back up when i put it in park? i pulled the dpfe sensor and cleaned the two hoses as they were really clogged up...any ideas? could it be the egr valve? anyw ay to test it?

 

[atvkid4eva]

ok so i juist went outside stuck a piece of tubing on the egr valve port and sucked on it with my mouth as hard as i could...it made the engine stumble but it didnt completely stall out..but prolly because my mouth couldnt keep eneough vaccumn..so i believe that means the egr valve is good?

 

[SMTGREG]

Find the EGR vacuum regulator valve there 2 wires going to it red and brown with pink. With the engine running ground the brown wire, that should apply vacuum to the EGR and cause the engine to idle very bad or stall. If it does the DPFE sensor is probably bad. If it doesn't change the idle check for vacuum leaks in the lines going to the EGR. It could also be restricted EGR ports in the intake manifold. When the PCM sets a code P0401 it will try to add more vacuum to the EGR looking for a change in voltage from the DPFE sensor. Normal voltage ranges from .2 volts EGR closed to 4.5 volts EGR open on the brown / light green wire. The truck will run bad then it will go into limp home mode (FMEM)

 

[fordman4488]

In my experiance, if you put vaccum on the egr manually you will kill the engine. EGR valves are not the hard to move the diaphram, and with it completely open it will stall every engine that i have messed with(especialy my 95 Explorer). I would test things first to make sure cuz it is free, but if nothing tests bad, try replacing the EGR valve because it sounds like the diaphram is bad or stuck.

 

[atvkid4eva]

well i replaced the dpfe sensor today...only time will tell if the check engine light will come back on...its still acting weird when i stop at a stop light tho the rpm it rise ans hold constant at about 1100 rpm and thats what it does before it will drop and stall out...any ideas?

 

[Jason]

Clean everything out before spending cash.

 

[atvkid4eva]

the new dpfe sensor seems to have shut off the CEL...and the bog and stalling at a stop seems to only happen with the heater on? i usually just use the floor heater so that my AC compressor dosent cyle..this is just a guess really ill have to give it some more trial and error with and without the heater on..is there any issues where the truck is sluggish with the heater on that you guys have heard of?

 

[Nhaz]

Truck bogging down with the heater on? That sounds like a alternator failing. Check voltage while at idle with and without the heater running. If its dropping below 12 at idle you have electrical power issues, either bad grounds bad alternator or bad regulator.

 

[atvkid4eva]

well im not 100% sure thats the cause of the bog, but it seems the heater has been on during the times it has bogged...and it idols fine except for when it has stalled at the stop lights..ill drive it today with the heater off to see if it changes anything.

 

[atvkid4eva]

ok so i thas nothin gto do with the heat..however my CEL did go off with the new sensor..i was driving home from work and at a stop light went to take off and there was a slight bog and then it drove fine the whole way home...also seems like the bog occurs on deceleration?

 

[atvkid4eva]

seemed to run fine last night until when i got back from going to the store and parked in my driveway i put the truck in park and right as i was about to turn it off i noticed the idle increased to about 1200 rpm stayed there for a second and then dropped way down and the truck almost stallled and then it picked back up to normal...could it be the IAC? are these symptom?

 

[Nhaz]

I have run my truck in the past without the IAC for almost 4 months. It just doesn't run well when its cold. I did eventually repair it. But it had no effect once the truck had warmed up. And only kicked in during the startup cycle. If you suspect the IAC is giving you trouble.

When the truck is starting to stumble. unplug the IAC. If the problem goes away almost instantly then clean or replace the iac.

 

[atvkid4eva]

i dont think theres enough time to unplug it when is starts to run bad..only happens when it is warm too.

 

[atvkid4eva]

ok so i just put a new TPS sensor in and the truck wouldnt even start....so i took it back off and put the old TPS back on and it still just cranked and cranked! so i took the old one back off any put the new one back on plugged it in and it finally started after about 2min or cranking...seemed to idol fine so i took it for a drive and it is running way worse than before with this new tps..it did the stalling thing about 3 times and would rev up high when i came to stop and sputted when i tried to go again and then when i shut it off it wont start back up easily at all...before i tried to replace this TSP atleast it started fine...is there a trick to intalling these TSP's?