Long time Lurker, First time poster

[I4CUTigers]

Hello! I have been searching this forum for years, gleaning advice on how to properly maintain and repair my 98 Explorer Sport SOHC.

Recently, however, I have been getting an Left bank lean code and after replacing both the PCV and the upper hoses, the problem persists. From everything I have read, the next step on the replace list is the upper and lower intake gaskets.

The questions I have for the board, is:

1) If I am doing this job, what other jobs should I go ahead and perform while I have the intake off (I am already going to replace the lower PCV hose, plugs and wires)?

2) What, if any specialty tools do I need? I do not own a torque wrench, so any recommendation there would be appreciated.

I appreciate your help. I own other vehicles, but this explorer is the only one I'm attached to. It was my first car and I really want to keep her going strong.

 

[I4CUTigers]

Bump/Update...

I can't seem to figure out the problem.

Original code: P0171, P0174

Repaired/Replaced/Fixed:
Upper and Lower Intake Gaskets replaced (Ford)
New Plugs (Bosch Double Platinum)
New Coils (OEM/Motorcraft)

Codes cleared for a while, then they came back

I then Fixed:
New IAC Valve (Motorcraft)
Reinstalled the old Mass Air Flow Sensor (Originally replaced this with a Duralast a few months ago when I got the first P0171 code)

I cleared the codes, and they haven't comeback, however, the car seemed to idle roughly when I would try to start it after it had been cooling off (but not cold).

I then installed a new Fuel filter. I thought it was better. I drove it. It seemed to respond better. But yet again, I let it sit for about 30 minutes and it was rough trying to start back up. Kept turning it off and on until the idle smoothed out.

Any ideas? I have a 98 6.0 SOHC with the VIS system.

 

[J_C]

I'd hook up a scan tool capable of showing live data, looking particularly at fuel trims... or anything else that sticks out if they aren't bad.

 

[Macgiobuin]

Check the fuel pressure. If you have the fuel pressure regulator in the fuel tank, then there could be a leak in the rubber hoses that enter/exit the pressure regulator housing, and if there is a leak in one of the hoses or the housing itself, you could be pressurized enough to start and even run when there isn't much of a load, like idling or cruising.

 

[I4CUTigers]

I'd hook up a scan tool capable of showing live data, looking particularly at fuel trims... or anything else that sticks out if they aren't bad.

Check the fuel pressure. If you have the fuel pressure regulator in the fuel tank, then there could be a leak in the rubber hoses that enter/exit the pressure regulator housing, and if there is a leak in one of the hoses or the housing itself, you could be pressurized enough to start and even run when there isn't much of a load, like idling or cruising.

I should have some time to run these tests tomorrow and post the results. Thank you all.

 

[I4CUTigers]

So I hooked up a new fuel pressure gauge at a cold start. In the on position, 25 psi (up from 10 PSI at OFF). Small dip during crank and again 25 PSI.

Once it was warm, repeated the test. In the ON position, 20 PSI. The car would not start (it had been sitting for 10 minutes.

I also hooked up blue driver. Couldn't get an accurate reading on fuel trims, but did see a P0231 code for "Fuel Pump Primary Circuit Low Input"

Ironically, I also got a stored P1260 code for "Theft detected, vehicle immobilized" and a P1000 for "OBD II Monitor Test Not Complete"

Any thoughts?

 

[Macgiobuin]

Your fuel pressure specification for '98 Explorer 4.0 l SOHC is 35-40 psi, and you're showing 20. Time to take the tank down and look at the hose leading out.

 

[RandomNerd2000]

Drop the tank, check the lines coming off the pump, probably wouldn't hurt to change the pump either as well as those lines if you haven't in recent years, or ever changed it. Sounds like a weak pump, I had this on my 01, made a whole bunch of weird issues too.

 

[I4CUTigers]

Drop the tank, check the lines coming off the pump, probably wouldn't hurt to change the pump either as well as those lines if you haven't in recent years, or ever changed it. Sounds like a weak pump, I had this on my 01, made a whole bunch of weird issues too.

I have a wholesaler close out Motorcraft pump coming in from Rockauto which I picked up the other day. Planning on dropping the tank this weekend. I just didn't know if an electrical gremlin could also be contributing to the issue?

I plugged my diagnostic scanner into my daily driver, it had no problem picking up that vehicles fuel trims, but there seems to be a lot of "vehicle supported" diagnostics on the Explorer that aren't showing any info when I run a live test.