2001 Explorer-Running out of ideas

[stevechaos]

Needing some advice, as I’m just about out of ideas with this truck.
It’s a 2001 with the 4.0, and right at 123,000 miles.
I bought it back earlier this year, replaced the front timing guides and it did fine up until a couple of months ago. I actually bought the vehicle for my mother and she was driving it the first time the issue occurred. According to her she was leaving the store and no matter how much she tried to gas it, the truck wouldn’t go above 30 or so MPH. She got about half way home in it and suddenly the power came back and it started driving like normal. When I got home from work and she told me about the problem, I went out, jumped in it, and took it for a test drive trying to replicate the problem. No such luck. It drove just fine. I still didn’t trust it though, so I parked it, planning to take a look at it when I had time.
Well, that time is now and we’re in a position where we need it back on the road. I thought a good tune up would get it back up to speed. No so luck. The first time I tried driving it from the yard to the garage I noticed the problem was a lot worse. It would start up and idle just fine. Give it some gas and it would move for about a minute, then start to hesitate and stop. It would still be running, but no matter how much you gassed it, it would not move. Turn the key off and back on and you would once again be able to move momentarily until the whole process repeated.
So far I’ve went ahead with the tune-up (plugs, wires, air filter, oil change)
Cleaned the MAF and IAC disconnected the exhaust at the Y pipe (in case the cats were clogged)
New EGR sensor (broke the old one taking out a plug wire)
Still it continues. It does seem to idle better (still low though, less than 1k) and will let you drive for a little over a minute before it seems to lose all interest in moving, but occasionally if you continue to rev it will kill back in and move again.
I’m stumped. I was pretty sure it was exhaust related, but the only thing left to be clogged would be the pre-cats. It’s weird; if you turn the truck on and let it run for a bit it will idle fine. Give it some throttle and once you release it seems to develop a miss and the idle speed drops to less than 1k.
Any ideas what else I might check?

 

[koda2000]

throttle position sensor maybe, or maybe a bad MAF sensor.

 

[jremington59]

If it were me I'd start with testing the fuel pressure.

 

[stevechaos]

If it were me I'd start with testing the fuel pressure.

Fuel pressure...that might make some sense I suppose.
I put some fresh gas in it last night, and let it idle for about 15 minutes. I could rev it up some and after awhile it would idle at about 1k. Problem is that if I rev'd it up to about 2.5k it would seem to suddenly miss, rev down and idle so low it would nearly die. It never did die though, I would give it a little more throttle, it would seem to wake back up a little as long as I was feathering the gas pedal, but as soon as I stopped it would idle real low again.
It's strange. It would start running almost right, I would put it in gear and go back and forth in the driveway and it would seem to do fine. Then I took it out in the field to open it up a little bit and it would get dicey again. Sometimes it would accelerate perfectly. Other times it would seem to miss and then finally after about 5 minutes it crawled to a stop and no amount of gas pumping would convince it to go again. Turned the key off and right back on and power seemed to be restored. At least long enough for me to drive it back into the shop.
I suppose it's completely possible that the fuel pump could be cutting in and out...I've just never known of one to do that. I don't usually work on stuff this new, but I kinda figured that it when a fuel pump went, it went. I've had fuel pumps go before, and they've just died. flat out failure. The fact that turning the key off and then back on confuses me too. It's like it resets something. Could it be the pump that it's resetting, or is it some stupid sensor somewhere?
Anyone have any suggestions on how to test the fuel pressure and TPS on this particular model? I know how to test a TPS on a chevy, but I've never messed with one on a Ford. I've never tested fuel pressure on a Ford before either. Has anyone done any write-ups on this site or elsewhere?

 

[jremington59]

Sounds completely logical that it could be a weak pump. Mine on my 5.0 acted up for a couple days before dying. Lack of acceleration, etc.

You need to get a pressure tester and test the pressure on the fuel rail. Just for the heck of it have you tried swapping relays under the dash?

If the TPS were faulty it should show a code. Is the CE light on? And you're idling to high.

 

[stevechaos]

Sounds completely logical that it could be a weak pump. Mine on my 5.0 acted up for a couple days before dying. Lack of acceleration, etc.

You need to get a pressure tester and test the pressure on the fuel rail. Just for the heck of it have you tried swapping relays under the dash?

If the TPS were faulty it should show a code. Is the CE light on?

The more I think about it, the more confusing it gets. The truck had a rough idle when I bought it. I figured it was probably due to the timing guide issue and the loose chain. But it didn't go away once I had replaced the guides. The clatter of the chain was the only change. I figured that it just needed a tune up badly.
Problem is that it's needed all the work I've done to it. Everything I've replaced needed replacing or cleaning and yet it still runs like crap.
Sounds like a plan to me. I'll check the pressure on the fuel rail, and do the relay dance and see what that gets me. Hopefully somewhere!

 

[jremington59]

I misspoke in my last post. The relay is in the power dist box under the hood.

I know I preach this a lot, but have you ever run injector cleaner through it? I read you did a tune up and assumed you changed the fuel filter. You didn't did you?

 

[stevechaos]

I misspoke in my last post. The relay is in the power dist box under the hood.

I know I preach this a lot, but have you ever run injector cleaner through it? I read you did a tune up and assumed you changed the fuel filter. You didn't did you?

Nope, no injector cleaner. I did change the fuel filter though.
My tune-up was plugs, wires, cleaning the air filter, changing the oil, cleaning the MAF and IAC, and replacing the EGR sensor. That's it, other than removing the exhaust past the pre-cats. Removing the cats DID seem to help with the idle. Pretty sure both of them and the pre-cats are bad. I was going to remove everything from the manifolds down to see what effect it had on the idle, but the bolts that connect the Y-pipe to the manifold are frozen up.
But I can't be sure that neither mom, or the guy I bought the truck from never ran injector cleaner through it.

 

[stevechaos]

Sounds completely logical that it could be a weak pump. Mine on my 5.0 acted up for a couple days before dying. Lack of acceleration, etc.

You need to get a pressure tester and test the pressure on the fuel rail. Just for the heck of it have you tried swapping relays under the dash?

If the TPS were faulty it should show a code. Is the CE light on? And you're idling to high.

The CEL is on, and it's been on since I purchased the truck. It was supposedly tied to the timing chain guides as per the shop that had been maintaining it for the guy I bought it from. That of course wasn't the case.
I haven't had it read since this all started, and I don't have a reader myself. I try to stick with pre computer vehicles personally, so I never invested in one.
How high should it idle? What's typical?

 

[jremington59]

It would really be helpful if you got the codes read. That could answer a lot.

As for the idle, when warm it should be in the 750 range.

 

[stevechaos]

It would really be helpful if you got the codes read. That could answer a lot.

As for the idle, when warm it should be in the 750 range.

trust me I know. Lol...
Problem is that it won't run long enough for me to get it anywhere and get it read. I live out in the sticks, and don't want to risk it leaving me stranded.
750 might be what it's trying to maintain, but it seems to loose it and fall below 5 most of the time.

 

[jremington59]

I've seen some little Acton scanners for 30 bucks that will actually read codes. It's all they do but it beats the hell out of the guess work.

 

[stevechaos]

I've seen some little Acton scanners for 30 bucks that will actually read codes. It's all they do but it beats the hell out of the guess work.

I bought a scanner, ran it and the only code I'm getting back is the one for the oxygen sensor that is disconnected.

 

[koda2000]

a bad (or disconnected) O2 sensor can cause the problem you're experiencing, as the ECU can't determine the proper fuel trims for the engine. start there.

 

[bandit11]

If it were me I'd start with testing the fuel pressure.

i agree apply the KISS principal and test the fuel pressure

 

[stevechaos]

Well, I have been messing around with the scanner and was able to pull the rich on bank 1 with lean on bank 2 as pending. I didn't log enough road time for it to fully load I guess.
From the research I've done on here that seems like a tell-tale sign of the shrunken o-ring/gasket problem, and an erratic idle has plagued this truck since I bought it. I guess now is as good of a time as any to go ahead and replace the gaskets.
Has anyone ever had similar problems prior to replacing theirs? I can sorta see how it could be the cause, depending on just how bad the seal is. If it's seriously screwing up the air fuel ratio that is. I
I know the gaskets need replacing, so I'm going to do it regardless, and see what effect it has.
That's the funny thing about this truck...it's needed all the work I've done, all the parts I've replaced were worn out and yet the problem persists...

 

[stevechaos]

So I finally got around to replacing the upper and lower intake gaskets last night. No noticeable change unfortunately. Like everything else I've replaced, they were shot and were flush with the edges of the intake. They were also hard as a rock and several tore when I took them out. I really figured that given their condition they would surely be a culprit. The dry line on the lowers was decent, but the uppers were almost all showing signs of leakage.
Frustrated by the lack of change, I threw in the towel after about 4 hours last night to regroup.
This morning I plugged my scanner in and ran Torque to see what I could find. There are no pending codes, no saved codes etc. However two things stood out; for one it said that the timing is 22 degrees advanced. Is that normal?
Also, the idle is LOW between 420 and 450. It will also dip and starve itself from time to time causing the truck to die.
I'm REALLY about out of ideas at this point. I don't have the equipment to check fuel pressure or compression, which are about the only things I haven't done. I'm debating cleaning the injectors (wish I would have before I put the intake back on) and seeing if that helps, but honestly I'm stuck.

 

[RomeovilleIL]

You really need to check the fuel pressure before throwing more parts at this. There is a schraeder valve next to the battery on the drivers side for checking fuel pressure. There is a tool made for checing the pressure but any of the cheap dial type tire air gauges will work to get a reading.

When the key is first turned the pump kicks on to prepressurize the system for maybe 3 seconds. Your 01 is a returnless system. Normal pressure is 65 psi. The engine can theoretically idle with about half that but will not rev or pull torque. If its anything under 60 the pump needs to be replaced.

 

[1992fordgreen]

Just replace the stupid fuel pump That is most likely the problem anyways.

 

[stevechaos]

You really need to check the fuel pressure before throwing more parts at this. There is a schraeder valve next to the battery on the drivers side for checking fuel pressure. There is a tool made for checing the pressure but any of the cheap dial type tire air gauges will work to get a reading.

When the key is first turned the pump kicks on to prepressurize the system for maybe 3 seconds. Your 01 is a returnless system. Normal pressure is 65 psi. The engine can theoretically idle with about half that but will not rev or pull torque. If its anything under 60 the pump needs to be replaced.

Well, I went ahead and cleaned the throttle body, checked for vaccum leaks, and did a few other misc tasks, and took her on a road test. Same thing. Adjusted the idle: same thing.
Grabbed a tire gauge, stuck it on that valve after turning the key on an bingo, 25psi. Tried the test again, got 35, then 45. I'm guessing that's why cycling the key on and off seems to restore power: everytime it attempts to pressurize the system it boosts the psi a little more each cycle.
I know how to replace a fuel pump. I hate doing it, but I know how. My question is which one to purchase? When I pull the pumps up it shows two different varieties; one with the completer sender unit and then one that's just a pump. Can the pump be replaced alone or is it permanently attached to the sending unit?