06 Explorer No DTCs hard start, rough idle, stalling

[marvelouzone]

Let me start by saying, I'm a diesel mechanic and know my way around Powerstrokes, this 4.0 is not what I would usually work on, but I have a friend who has 2006 explorer 4.0L SOHC, someone told him he needed a motor with out explanation why, so I didnt want to see him get ripped off. The problem is it idles very rough, hard to start, and stalls. There's no DTCs , if you hold the accelerator slightly it will stay running, but once you let off it will either idle really bad and misfire or cut off, once pushing the accelerator the rpms raise very smoothly up til 3500 which is what I assume the rev limit is in nuetral. I've done checks with focom and forscan, I was thinking possibly a bad fuel pump, while monitoring fuel pressure I see a range of 289 - 326 kpa with 26% fuel pump I guess duty cycle would be the correct term(once again I'm a diesel guy, and use to dealing with IPRs and Hpops) not sure if the desired fuel pressure is relevant on these but it always stays at 269kpa. I believe that equals out to 40-48psi while I believe this system is supposed to have somewhere in the range of 60 - 70, but I wouldnt expect to get a rough idle with no load with almost 50 psi of fuel pressure.

so with no DTCs Im baffled, and dont want to start waisting money just throwing parts at it. I've thought everything from fuel pressure sensor, to coil pack(replaced 4 months ago) to crank and cam sensors

I need help, Ideas, guidance, something. lol

I did end up getting a code p106, but I believe this is because I didnt tighten the intake hose after checking the throttle bottle, I just slid it back on. out of the 4 days of testing first time I seen a code pop up besides unplugging some sensors here and there to make sure the pcm would actually register a dtc.

 

[SteveOReno]

Rough idle can be caused by the computer (PCM) messing with the fuel trims, which is usually caused by a misfire engine code or something similar. The software in the computer does not handle faults well and can make things worse, then not be able to recover, so once you are in fault mode things get worse and worse. Even clearing the DTC engine codes will not bring it out of fault mode. The engine codes could have been cleared before you got the car. The solution is to disconnect the battery and discharge the computer capacitor by applying the brakes to drain the residual charge, or leave the battery disconnected overnight. This will reset the PCM and clear the fault mode.

 

[marvelouzone]

Rough idle can be caused by the computer (PCM) messing with the fuel trims, which is usually caused by a misfire engine code or something similar. The software in the computer does not handle faults well and can make things worse, then not be able to recover, so once you are in fault mode things get worse and worse. Even clearing the DTC engine codes will not bring it out of fault mode. The engine codes could have been cleared before you got the car. The solution is to disconnect the battery and discharge the computer capacitor by applying the brakes to drain the residual charge, or leave the battery disconnected overnight. This will reset the PCM and clear the fault mode.

When the tow truck dropped the vehicle off the battery was disconnected, and stayed disconnected for 2 days before I started trying to diagnose it.

Do you know if the fuel pressure desired pid should fluctuate? because when I check the live data it stays constant

 

[SteveOReno]

I don't know if the fuel pressure should fluctuate, but if the engine runs well at higher rpms then that means it is getting plenty of fuel. I guess the fuel pressure could be too high at idle? Would a loose timing chain flop around at idle but tighten up at higher rpms?

 

[Gorb]

Mone does that if I start it with the wheels cranked to the left.

Not sure what that means but maybe that could point you in the right direction

 

[marvelouzone]

Mone does that if I start it with the wheels cranked to the left.

Not sure what that means but maybe that could point you in the right direction

Yours does what?

 

[Gorb]

Runs rough, sputters and wants to die

 

[Gorb]

Yours does what?

Basically what I'm trying to say is I can recreate your problem on my truck by parking it with the wheels cranked all the way to the left, shutting it off, and starting it a few minutes later.

The vehicle you speak of seems to be stuck like this... so if we figure out what's under load in that situation we could potentially solve the problem

 

[marvelouzone]

Bump anymore suggestions?

 

[Gorb]

Test the battery and alternator?

 

[timbit]

I just got an 04 NBX with the 4.0 doing the exact same symptoms, very rough idle, have to hold pedal down slightly to keep running, has some engine noise im thinking is timing chain problem possibly, and revs to 3500 and smooth then, stumbles back at idle and no codes show up on scan.....marvelouzone, ever figure it out??? Or anyone ideas??

 

[Beachcomber86]

Check these two things before you start spending lots of money on parts.
1. Found my ghosts in the machine
2. Check the evap hose from the manifold to the valve. If it turns your fingers black when you rub it, replace it. It is probably leaking a little but not enough to throw a code.