Cant seem to find the true answer to this problem

[mikeonabike]

Ok, first and foremost i have found many forums talking about similar issues and fixes for them but they are all for different engines/different year models/ different generations. all of which dont seem to apply to my engine/model setup. if you know of a forum that covers these problems please direct me to them, i have scrolled through about 20 pages on this group and cant find the exact problem/solution to my problem so here goes, hopefully the explorer guru has a helpful solution for me

my explorer has a little over 200,000 miles on it and has lived a fairly easy life with a decent effort in maintenance but nothing over the top in regards to care, about 10,000 miles ago a idle problem started to rear its ugly head every now and again where if it got any where near 500RPM it would just drop RPM and die. the car drives fine as long as it stays above 1000 RPM. so when going down the road there is no power loss, no stuttering no issue at all. highway driving is completely fine and actually runs really well when going down the road. it will run and drive fine for a few days with no issue then one day it will bounce its idle from around 300RPM to 600RPM but as soon as you take off it works fine, it accelerates fine it shifts fine, no issue to be seen till you take your foot of the gas and let the idle drop then it will just die becasue the RPM dropped too low. when it starts to do this RPM bounce it will eventually lead it just killing itself entirely when it tries to idle. now i have seen people talk about the fuel pump could be bad but other than the p0193 code i dont seem to find any other characteristic of its performance to believe that is the problem. I have seen others post about how it could be a vacuum leak but every post people where people discuss that is for the previous engine before 2005. the vacuum line they seem to point out i cant seem to find on this engine. I have also seen people talk about how the throttle body needs to be cleaned or replaced but again this seems to be a solution for the previous engine, not the SOHC 4.0 I am fairly mechanically inclined and just replace the valve cover gaskets and intake gaskets so i am fairly capable for a drive way mechanic. I am really hoping that someone on here has the answer for me so i can slap myself and say "DUH!" and drive this thing without worrying about it dying. below are some more details of other problems that could relate to what is going on.

1. car pops a P0193 code occasionally, i know this is a FPS problem and from everything i have read it doesnt affect drivability of the car at all but i figure that needs to be on the list.
2. a P0506 code will pop when the problem kicks in but goes away ass soon as the car starts working fine again.
3 no power loss at all and as long as it stays above 1000RPM you would never know there is a problem
4. the problem comes and goes. it can drive fine for a week and then just screw up for no reason
5 weather doesnt seem to affect it neither does drive time or engine temp, at least i have yet to find a commonality when the issue pops up.
6 the engine has a throttle body spacer on it and a K&N air filter but these problems were happening befoere those were installed.

if you have any question please ask them i will be checking this post fairly regularly because i have a long drive coming up for the holidays and i would love to get this solved before the trip. thank you everyone for reading this long post and any help you guys and gals can offer.

 

[spbagwell]

For what it is worth, I had something similar to your issue where moving down the road or on the highway the engine ran smoothly. I was still getting 20 mpg on the highway. However, if my 2010 Explorer was stopped, sometimes the engine RPMs would fluctuate between 500 to 800. This would occur for about 5 mins then return to normal RPMs. After a few minutes, the fluctuating RPM issue would return. It never stalled when stopped, but the engine did cut off a few times when slowing down in 1st gear. The Check Engine Light was on and the codes were rampant. One day it would be 2 codes; the next day, there would be 12 codes. When the PCM was reset, a new set of codes would appear. Oddly enough, the a/c condensor would come on and off instead of remaining on continuously.The Service Dept at a Ford dealer could not isolate the issue after several tries but recommended the PCM be replaced. It was not a cheap option but chasing codes was worse. Since the PCM was replaced a week ago, the engine has been running smooth and the a/c has been consistent. I took it for a 1,000 mile road trip with no issues.

Looking back, the fuel pump was replaced a year ago (engine would turn over but not fire). The EGR valve was replaced a month ago. The PCM was the last thing I suspected as it is difficult to isolate, but I replaced one in a 1997 Expedition as well when the engine would unexpectedly die. It is not good news, but provides an option to consider.

 

[Explorer_PL]

Can you see live data numbers ?

O2 voltage on both banks, fuel trim numbers ?
Vacuum leak maybe ?

 

[Littleant]

Back in the olden days when I did auto repair ( for 35 years) this would be a classic example of a vacuum leak as mentioned by Explorer pl

 

[michael loibl]

Sounds like vacuum leak or EGR stuck open, but since u did the egr already id suspect a vacume leak.

Last year I was certain I had a bad EGR valve, but it ended up being a nasty idol vibration due to a partially broken harmonic balancer. But my rpm was not dropping, just lumpy idle

 

[Greg_DonWindsor]

I had an older 4.0SOHC, and fixed it’s rough idle with a new idle air control (IAC) valve, new fuel pump, and fuel filter.

 

[Beachcomber86]

Check the evap hose too. $2 fix to replace.