I've got a 2004 Exploder 4X4 with the FlexFuel 4.0L V6 126,xxxish Miles
Last Monday i noticed that the x was idling rough around 500rpm. While in park or driving.
I spent Wednesday looking for vacuum leaks with carb cleaner, cleaned the MAF, Changed the Hose that runs from the intake to the evap purge valve thinger.
Broke off the two torx head bolts holding the TPS on and had to buy a whole new throttle body($400FYI)
Installed the new throttle body and fired it up. it idles around 1000 for a few seconds then drops to 500 ish rpm. While the rpms are coming down it runs as rough as it did before..

Its been a real tiring day trying to figure this one out. any help would be appreciated.

Thursday update= I've filled it with premium gas and added a bottle of gas dryer to the tank and still idling like crap, drives fine though.

 

Two thoughts....clean the throttle body valve (both sides) just inside the round opening; clean or replace the IAC valve (idle air control). I had erratic idle til I bought a new IAC.

 

If like my 04 Mounty , your 4.0 is drive by wire . So no IAC valve . You replaced the throttle body , that does the Idle air function . Do you have any codes ? Do you have excessive engine noise , Timing chain issues ? A bit more info on the symptom please .

 

yes it is drive by wire, no noises, no codes. a buddy at work thought it might be a fuel injector problem.. so i pulled the electrical connection off of No.1cyl injector(only one i could reach easily)...no change in idle.

Now i maybe rusty on my automotive fuel injection systems but its not supposed to fire the injector with no electrical input?

 

Correct . If injector unplugged , it should start to miss . How is power while driving ? Fuel pressure good ? If flex fuel there is a fuel filter hidden behind a cover on the pass side in front of the tank . What are your fuel trim numbers and mass air flow readings at idle and full throttle ? A bad MAF can cause your complaint as I read it so far . A good scanner , not just code reader , would be helpful .

 

Power is fine while driving/ above 1000 rpm.. I dont have a pressure gague to test fuel pressure but. yes it is a flex , I had the fuel filter changed about 1 1/2years ago.

I will try to get a hold of a scanner tomorrow. When i cleaned the MAF it wasn't dirty to begin with...i used about half a can of the CRC MAF sensor cleaner.

 

The MAF does not have to be dirty to be bad . A scanner will help narrow down your issue . Oh , In my opinion , the fuel filter should be changed at least once a year or 20-25k whichever comes first . Let us know what you find .

 

Took it to the shop saturday and they scanned it....found misfire in two cyls. Which i found odd as it did not throw a check light. I should have it back monday afternoon.

 

Wasn't a miss fire...shop put it on three different scanners and only the snap on on said it was a miss fire.

They cleaned the injectors with a ford recommended cleaner and that helped a bit, tried to enrich the fuel air mix with no results. They checked compression in all the cylinders and preformed a vacuum leak test. They replaced the vibration dampener and still no improvement. Re flashed the computer to the latest program and that seemed settle the problem. now the vibration comes and goes... only while in the 600 to 1000rpm range.


better than it was, but not as it was before.

 

The Snap-On scan tool may have been the only one that was monitoring PIDs and for pending codes. My OTC Genisys helped me find numerous failing CoPs with the same feature, checking PIDs for individual cylinder misfire counts. That would identify a failing CoP when I started to notice a rough idle and long before a diagnostic code would be set. I wouldn't give up on the chance of misfires on the two cylinders identified by the Snap-On yet.

-Rod

 

I broke down and took it to the ford dealer...bad harmonic balancer and the new throttle body i put on was not reading correctly so ford replaced that under warranty.