Engine losing power / oil gauge going nuts

[Daniel V]

2000 4.0 SOHC XLT 224K Miles.

Using the cruise control on the way home from work and it started to decelerate. Tapped the gas and everything seemed fine. Stopped at the store and the idle started dropping below 500rpms. I checked the oil after getting out of the store and it was fine. About six miles down the road and after a big hill started losing power and the oil pressure gauge started going nuts. Shut it down and pulled off the road.

I didn't hear any gnarly noises while this was happening. The temp gauge was at 1/2 like it always is. I'm a few hundred over due for an oil change and I did not change the filter last time (couldn't get the sucker off)but the mobil1 I use says good for 10k so I thought another 3k would be alright. It was about 105 out today.

Any thoughts on what direction to start it would be great.

Thanks.

 

[410Fortune]

Yes, you need to check for fuel pressure first thing
It sounds as if you may have lost a fuel pump

When you first turn your key you should hear the pump run for just a second or two... the pump is located in the tank just below and behind the drivers door....try listening, sometimes you can hear good by removing the fuel cap, have somebody turn the key for you.

Next if you hear a pump run, you can test fuel psi at the fuel rail your truck should have 64 psi to start and run properly

The oil gauge going nuts is likely just because the engine was stalling out and oil pressure was dropping
The oil pressure gauge is not much of a gauge, more of a switch. Meaning some oil pressure the gauge reads in the middle. It is not an accurate indication of actual oil pressure

 

[Daniel V]

Yes, you need to check for fuel pressure first thing
It sounds as if you may have lost a fuel pump

When you first turn your key you should hear the pump run for just a second or two... the pump is located in the tank just below and behind the drivers door....try listening, sometimes you can hear good by removing the fuel cap, have somebody turn the key for you.

Next if you hear a pump run, you can test fuel psi at the fuel rail your truck should have 64 psi to start and run properly

The oil gauge going nuts is likely just because the engine was stalling out and oil pressure was dropping
The oil pressure gauge is not much of a gauge, more of a switch. Meaning some oil pressure the gauge reads in the middle. It is not an accurate indication of actual oil pressure

I was able to start it and drive it about 8 miles to park it at my girlfriends house this morning with no issues. I'm going to pick up a fuel pressure gauge today and will report back after I get off work. Thanks for the reply.

 

[410Fortune]

Pretty common for a pump that is getting older to start acting weak when hot and then return to building pressure when cold
Still sounds like fuel pump!
When they get hot they can no longer keep up with demand and the fuel rail pressure starts to drop off until your engine just cannot run anymore

the fuel pressure gauge will tell the tale

 

[donalds]

I vote for fuel pump overheating

 

[donalds]

Here is what your in for

Is my fuel pump bad 1999 ford explorer shoc 4.0. Lots of pictures on the replacement

How can I explain this

www.explorerforum.com

 

[Daniel V]

Getting a good reading on the gauge.

It's been sitting all day so it definitely is not the same conditions as when I was having the issue.

Thoughts?

 

[donalds]

Test it after a drive when it's hot. Imo

 

[BTR]

Measure the fuel pressure "live." Make sure the gauge is connected to the rail SECURELY! No leaks! Then, secure the gauge and hose somewhere out of the way of the hood when closed. Maybe on top of the brake booster. Zip-tie it in place. Then, drive until engine is hot. Pull over somewhere where you can raise the hood. Leave the engine running and read the gauge. Shut the engine off and read the gauge. Shut the hood (to retain "normal" heat). Every 15-minutes come back, open the hood, read the gauge, and shut the hood. Get readings at 0 ON, 0 OFF, 15, 30, 45, and 60 minutes.

 

[Daniel V]

Measure the fuel pressure "live." Make sure the gauge is connected to the rail SECURELY! No leaks! Then, secure the gauge and hose somewhere out of the way of the hood when closed. Maybe on top of the brake booster. Zip-tie it in place. Then, drive until engine is hot. Pull over somewhere where you can raise the hood. Leave the engine running and read the gauge. Shut the engine off and read the gauge. Shut the hood (to retain "normal" heat). Every 15-minutes come back, open the hood, read the gauge, and shut the hood. Get readings at 0 ON, 0 OFF, 15, 30, 45, and 60 minutes.

Okay I will do this after work today

 

[Daniel V]

Drove it around for about 30 minutes, some in town and some highway. Here is what I got:

0 On

0 off

15

30

45

60

Not sure if this is good or bad.
Thanks for the replys so far

 

[BTR]

Here's a summary of your findings:

0 Mins, Hot Engine, Engine ON - 65 PSI
0 Mins, Hot Engine, Engine OFF - 64 PSI
15 Mins, Hot Engine, Engine OFF - 62
30 Mins - 46
45 Mins - 32
60 Mins - 24

Based on your data, my takeaway is that your fuel pump is OK. However, having said that, it's known that in the early stages of a fuel pump going bad, it can misbehave randomly, i.e., there's a chance your pump was behaving when you gathered this data... and data gathered at some other, future time could in fact reveal a bad pump.

I don't want to send you on a wild-goose-chase checking all kinds of things, but have you checked all of your electrical grounds to make sure they're making solid contact and no ground wires are frayed?

I'm interested to hear what @donalds and @410Fortune have to say. They have a lot of experience. Hopefully, they'll reply with their insights.

 

[donalds]

I say that pump is weak or on the weak side a healthy pump will read 67-69 your numbers are a little low which does matter
I'd replace it
It's also bleeding down overnight = hard starting in the morning
Imo

 

[MrQ]

A little bleed down is normal, that's why the fuel pump runs a few seconds on KOEO to re-pressurize the rail. Dropping that much in an hour is not too bad, but I am leaning toward a bad check valve here. On the later return-less systems 99-up the fuel system relies on the check valve in the fuel pump to keep the system pressurized rather than the vacuum style fuel pressure regulator that is on the return style. These are known to fail after a while. So the pump may be putting out the pressure, but the check valve may not be keeping it there.

 

[410Fortune]

I do not think the fuel pump is the cause for concern, not with those numbers.
I would call that a healthy pump, 65 psi at idle when warm = good to go.
I have seen fuel pumps bleed down pressure in 10 minutes and the truck still starts and runs fine...

Now I would LOVE for you to keep that PSI gauge handy, get the truck hot until it has issues running and idling and then install the gauge again.
See if the fuel pressure drops off when hot
30 min of driving may not have been enough
But so far all the fuel PSI tests you have done are showing good fuel pressure

So lets start looking at other possible causes:

Do you have a check engine light?

How many miles on the 2000 SOHC and transmission? EDIT NM I see 224K miles

Could this possibly be a transmission issue? losing power on a hill, bucking

Has the truck done this again or was it just the one time while using cruise?

 

[974X4BLACKSPORT]

I would install new ends on those positive battery leads ASAP!

 

[Daniel V]

@donalds I wouldn't mind tackling this job but hopefully I can avoid it. The write up you did seems like it would be enough to guide me.

@BTR Just get a wire diagram and start checking all the connections? I have not had any electrical issues besides the radio display fading on and off at its leisure.

@MrQ What would be the process for checking on this valve? Seems like you said its in or near the fuel pump so that doesn't sound like I could easily access it.

@410Fortune The CEL has never worked. I bought this about 1.5 years ago from an older couple and it still had the original sticker w/ the price in the glovebox so I didn't think it was anything malicious. I just have never gotten around to finding out why the light was not working. I have not had any MAJOR issues with this truck. I discovered early on that if I did not let it warm up it would flare and not want to shift into second, but I just treat it real good and always give it 10 or so minutes before I try to drive it. It shifts a little rough into 2nd but not anything that is out of the norm with how many miles that it has I don't think.

This is the first time that something like this has happened. I had driven it about 25 or so miles on the highway on the way home from work when I noticed that it was slowing down while using cruise control without me pressing the brake or anything. It was just a slight slow down and it did downshift and accelerate back up to the 65 I had set it to when I gave it some gas. It then acted like it wanted to die when I parked it at the store about 2 minutes later... RPMS falling below 500 and then revving back up a bit to recover. I was in the store for about 20 minutes or so before I started on my way again. After I made it to the top of the hill and was driving on flat land for about 1.5 miles it really started to lose power and then the oil gauge started going nuts. So I parked it and drove it back into town the next morning.

I wouldn't mind driving it around for hours trying to recreate the issue. The gauge is a loaner that I have to return tomorrow but I'm sure they would let me borrow it again. The weather is alot cooler here then it was the day that it happened so I'm not sure I would be to accomplish that. It was 105 that day and it has been 15 - 20 degrees cooler each day since then.

It has seemed to me that the idle has always been a bit on the low side... I still need to replace the intake manifold gaskets because it has that issue with starting when it is cold outside and I sort of thought that had something to do with it.

I'm going to borrow a code reader from work today and see if I get anything. I'll report back with that once I'm off work.

@974X4BLACKSPORT I'll get some and do that! Thanks

Thanks to all the replys. I really appreciate the insight here. Although I'm not the most mechanically inclined person, this site and its members are always extremely helpful.

 

[Daniel V]

P0300
P0171
P0174

I did the plugs and wires about 10k miles ago. I'll start working on some of the other things this weekend.

The intake manifold gaskets are in pretty bad shape too. I imagine that could not be helping much. I bought the parts but the job seemed pretty daunting so I've been sitting on them for 6 months.

 

[donalds]

It's not hard
Plus you got us

 

[BTR]

My apologies. My previous comment re "electrical grounds" wasn't clear.

What I mean by "Have you checked all of your electrical grounds to make sure they're making solid contact and no ground wires are frayed?" is to check the locations at which the positive and negative battery cables are connected, the locations at which the engine is grounded to the frame (usually this is a grounding wire/cable), and the cables/wires associated with these connections.

What I don't mean is what you asked about doing, i.e., get a wiring diagram and check all of the connections. Due to the sheer number of connections, this would be an incredibly challenging task. Thus, for now, just check the connections I listed above.

Re replacing the intake manifold gaskets, you might consider the following. Your truck has a lot of miles, and years, on it. Given this, there are some things that are known to go bad over time. Thus, if you're going to do repairs, it begs the question: How long do you plan to keep your truck? Specifically, if you're going to take everything apart that's required to replace the intake manifold gaskets, there are several other parts that could (should?) be replace while you have everything torn apart. Once you're "in there," it's (almost) a no-brainer to replace several of the O-rings, the PCV valve, the fuel injectors and associated gaskets/O-rings, the temperature sensors, and thoroughly check the plastic intake manifold for cracks. These are all parts that are known to break sooner or later.