Ugh... 92 Explorer Hell..

[MistahYebba]

Fuel filter is a good maintenance item, especially if the history is unknown. I replaced mine when I got it, I knew the previous owner did it but I didn't know when or how many miles ago. Keeping records is nice.

I replied to your other thread. This just keeps on getting more and more interesting

I hope I take the fuel filter off and it's crusty and old and terribly goopy.. 'cause at least 1% of my problem would lie there in that case!

Any idea where the inertia switch is? I thought it might be near the PCM... not sure if that's it though. I could unplug the fuel pump relay but that's too much work. And I have no idea which fuse it is. I bet it's printed on the bottom of the PBD lid but... I'm not there right now.

 

[natenkiki2004]

No need to run the fuel system dry, there won't be much fuel that comes out. The majority will be in the fuel filter itself.

 

[MistahYebba]

So.... I go to change my fuel filter.. Easy enough, right?

WRONG.

This is what my filter line looks like....

So....

How the heck, right?

I got one of those "special removal tools" to make it easy...

The freakin' tool doesn't fit between the filter and the push lock thing..

So I cut it down hoping it would work (albeit cut very jaggedly...)...........

Ugh, this is the result.. NOT EVEN CLOSE.

Maybe I'm a freakin' moron but I reckon my filter lines are... unique...

-----------

Back to the MAF thing...

After doing some research, I'm convinced that the MAF doesn't have a 5v reference. Correct me if I'm wrong?

http://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/maf-sensor-tests-4

Check out that guide.

It says Wire C is a ground and should output 12v?

However, it says to probe the sensor with the negative and probe the positive battery terminal with the positive lead.... I was doing it in reverse and getting like .2v... I wonder if I flipped it around would I get 12v?

If so... then my MAF sensor would be fine I reckon..

And if my MAF sensor is fine... and my TPS is giving me the proper 5v reference... and my fuel filter looks good on the outside the way that it does.. (still gonna replace it if I can figure out how..)

Then...

Well damn....

 

[natenkiki2004]

Maybe the MAF does run on 12v, I've not measured mine. I thought they all ran on the 5v reference.

Wire C being a ground, it won't output anything. When you probe it with the black probe and touch the red probe to battery positive, you're measuring a difference in potential. Nothing is flowing or being outputted.

When you have leads in the wrong polarity, the multimeter will add a - to the display, indicating negative (unless you have an analog multimeter). It has no effect on VDC readings, just that it's "negative" voltage. If you truly got 0.2v by probing the ground, you have computer issues or wiring to the computer issues.

At this point, you should really invest in the EVTM book for your 1992. You're going to have to start digging. If your readings are correct so far (6v on the MAF, 0.2v on ground) then you're going to want to start probing at the computer to see if it's a wiring issue or computer issue. The MAF should get power and ground from the computer, if you probe the outputs of the computer and the readings are correct, you have wiring issues. If the computer's output is bad... I think you know the answer.

 

[MistahYebba]

Maybe the MAF does run on 12v, I've not measured mine. I thought they all ran on the 5v reference.

Wire C being a ground, it won't output anything. When you probe it with the black probe and touch the red probe to battery positive, you're measuring a difference in potential. Nothing is flowing or being outputted.

When you have leads in the wrong polarity, the multimeter will add a - to the display, indicating negative (unless you have an analog multimeter). It has no effect on VDC readings, just that it's "negative" voltage. If you truly got 0.2v by probing the ground, you have computer issues or wiring to the computer issues.

At this point, you should really invest in the EVTM book for your 1992. You're going to have to start digging. If your readings are correct so far (6v on the MAF, 0.2v on ground) then you're going to want to start probing at the computer to see if it's a wiring issue or computer issue. The MAF should get power and ground from the computer, if you probe the outputs of the computer and the readings are correct, you have wiring issues. If the computer's output is bad... I think you know the answer.

Well what do you think about that MAF test website I sent you that says I should get 12v on the first wire backprobing with the red lead, and 12v on wires 2 and 3 backprobing with the black lead?

Also, if you want something interesting... if I get a good backbrobe on the MAF and have a steady voltage; that voltage disippates when I plug it in.

I told you I have 6v on wire C... well that 6vs drops to .2v immediately when I plug it in. This might be normal.

However, I haven't mentioned I actually did get my power to the MAF correctly. All 12V from the battery at Wire A... I'm going to test Wire B and Wire C backwards.. (backprobing with black instead) and see the results. Standby.


Oh yeah, and last night my hood stopped latching... It just stays open now :/ something must have broke off but I don't know what. The latch looks fine. Is there supposed to be some hooky thing on the underlip of the hood or what? :/

 

[MistahYebba]

Soo..

Bit of an interesting update today.

After changing my fuel filter yesterday, I tried to start the car right away.

As you can imagine, there's no fuel in the lines, so it didn't start.

I figured I'd use my common sense and turn the key on and off a few times to let the fuel pump run multiple times until the lines were "full"

(any damage to be done doing this on already full lines?)

Upon starting my car after doing this sort of "priming".... what do you know, the car ran spectacularly!

I was pretty excited as you can imagine, because I thought maybe the fuel filter was the fix... which sounds crazy.

But anyway, it was running great.. everything was plugged in.

I decided to take it for a test drive but about 50% of the way to the station it started acting up again.

---------

Now remember; when my fuel pump relay was loose and I could punch my PDB to make it activate (for whatever reason), I told you that I punched it 6-7 times to let it pump through and "prime" it.. and it also ran like a dream then too! But it was short lived.

What does this tell you???

Because it tells me that turning the key on and off to let the fuel pump activate a bunch of times must be filling something up that isn't normally being filled up?

And it runs like a dream until it gets drained again.

If that makes sense.

------------

Now take this into consideration.

If I start it up right away without "priming" it and the IAC plugged in, you know it wants to stall.

Well...

If I hold the gas pedal down at about 1500RPMs, it'll sound like someone revving a motorcycle between 1k and 2k RPM back and forth.

If I keep my patience and continue to hold the pedal at 1500RPMs for a minute or 2... it'll all the sudden rev real high by itself to like 3k.. and then fall back down and actually kinda work... and stay at 1500RPM like it's supposed to.

On top of this, if I'm holding it at 1500RPMs and it's doing that 1k-2k surging, I can rev high like 3k RPMs and it holds 3k just fine. I wonder why..

 

[Bobmbx]

Did you solve the loose relay issue?


Get a multimeter on the wires to the fuel pump and see if you detect a voltage fluctuation. You may not be able to get to it at the pump, so look for the engine-side of the fuel pump power cable.

 

[MistahYebba]

Did you solve the loose relay issue?


Get a multimeter on the wires to the fuel pump and see if you detect a voltage fluctuation. You may not be able to get to it at the pump, so look for the engine-side of the fuel pump power cable.

Yes, punching my PDB no longer makes the fuel pump activate so I guess taking everything out and re-seating all the connections fixed that issue.

If I had a voltage fluctuation, how come it would work only sometimes and not other times? On top of that, why would it stop fluctuating by unplugging the IAC?

Do you think what I was saying about letting it "prime" is a logical explanation?

**edit**

I want to get more solid results on that. If I can learn what actions I have to take to make the work well, and be able to recreate my "fix" on demand, it think I will have narrowed down the problem greatly.

Therefore, when I get the chance, I am going to plug the IAC in and turn the key on/off 15 times (therefore activating the fuel pump 15 times), and then start the car and see how it runs.

Then I'll run if it's running good until it dies out and then repeat.

If I can do that and get the car to run good, we know it must be fuel related.

 

[natenkiki2004]

Because it tells me that turning the key on and off to let the fuel pump activate a bunch of times must be filling something up that isn't normally being filled up?

And it runs like a dream until it gets drained again.

If that makes sense.

The only thing this might temporarily fix is a bad fuel pump and/or fuel pump relay OR fuel lines that have drained from a faulty check valve in the fuel pump. The computer controls the fuel pump so as long as there's a crank signal (engine is running) then the fuel pump is on. Priming the pump will only help starting, it won't help running.

Yes, punching my PDB no longer makes the fuel pump activate so I guess taking everything out and re-seating all the connections fixed that issue.

You shouldn't guess with electrical work. Either it works 100% and is reliable or it doesn't work. In order to know that it's reliable, you need to find the cause of the problem and permanently fix it. Can you imagine a mechanic telling you "yea I punched the PDB and I guess it works now".

If I had a voltage fluctuation, how come it would work only sometimes and not other times?

A good way to tell voltage fluctuation issues is to check fuel pressure and then go around shaking the wiring harness and relays to see if that changes in the slightest.

On top of that, why would it stop fluctuating by unplugging the IAC?

I think you're depending on explanations that covers everything entirely. Like I said, the IAC is probably unrelated, a victim of the problem. Unplugging it is doing something that masks the underlying problem, not fixes it. Hell, going back to voltage issues, maybe it's the driver's in the computer that are failing or weak and unplugging the IAC means less load on the computer?

I want to get more solid results on that. If I can learn what actions I have to take to make the work well, and be able to recreate my "fix" on demand, it think I will have narrowed down the problem greatly.

Therefore, when I get the chance, I am going to plug the IAC in and turn the key on/off 15 times (therefore activating the fuel pump 15 times), and then start the car and see how it runs.

Then I'll run if it's running good until it dies out and then repeat.

If I can do that and get the car to run good, we know it must be fuel related.

Now you're thinking right. However, I'd make a few changes. 15 times is overly excessive and won't do anything for you. Even if your entire fuel line is emptying, no more than 5 times should do it. I had my engine out for a week, the fuel rail was bone dry and I imagine the lines were fairly empty. I think I primed twice and it fired immediately.

As I said above, it's not really a fuel issue, but leans heavily on a fuel delivery issue. Voltage drop, shorting, bad fuel pump, bad fuel pump relay. You're going to have to get comfortable in testing electrically if you do end up going down this road.

 

[MistahYebba]

I liked this big reply Nate. Very thorough.

Think of my little priming solution theory this way.. (don’t mind my comical approach to “fuels”)

If the engine consumes 5 fuels per second, and the fuel pump is supposed to provide 5 fuels per second, it balances out, therefore always having a constant and equal supply of fuel.

If there is a problem in the engine and it’s consuming 6 fuels per second, and the fuel pump is perfect and still pumping 5 fuels per second, eventually, the fuel available for the engine will run out.

Adversely, if the engine is working correctly and consuming 5 fuels per second, but the fuel pump is malfunctioning and pumping 4 pumps per second, once again, the engine’s fuel will soon run out.

If there’s some sort of reservoir at the end of the fuel lines that the fuel pools into, but the fuel pump is malfunctioning and only pumping enough to fill the lines and not that reservoir (while the truck is running), the only solution would be to FORCE it to fill that reservoir.. (i.e. fill it while the engine isn’t consuming fuel at a faster rate than it’s pumping out).

So, you would add fuel, add fuel, add fuel, add fuel, add fuel, and now the reservoir would be full.

However, after a short time of running, the fuel pump wouldn’t have been able to keep up with the engine consumption rate and therefore the reservoir would become empty again.

This all sounds crazy, but this is how I’m imagining it happening in my head. I’m probably wrong but I wanted to explain my crazy thoughts.

------

What you said about the voltage thing and having the IAC plugged in makes complete sense.

But then I would wonder why I can’t unplug the MAF sensor instead to make my car driveable? And why only unplugging the IAC gives me those results??

Cause if it was a case of having a limited supply of voltage to take out, and unplugging the IAC allows more voltage to go into the reserve, that would mean in theory I would be able to keep the IAC plugged in and unplug something that takes up MORE voltage than the IAC and get even better results

and I’m pretty sure the MAF takes up way more voltage than the IAC. Could be wrong about that though.

----------- moving on..

I just feel if it was an electrical issue, I wouldn’t be able to turn on my car one second and it stalls instantly, and then at the next moment, turn on my car a second, third, or fourth time and all the sudden it’s running perfectly.

AHHHHHHHHHHHHHHHHHHHHHHHHHHH

Hey so I hope you’re having a good Thursday

 

[MistahYebba]

As for the whole “guessing” thing…

Well, I can tell you for sure that punching my PDB doesn’t make the fuel pump activate anymore. That means I fixed it lol.

I said “I guess” because I couldn’t believe something as simple as pushing back in a loose relay would make the fuel pump stop activating when you punch it with the key in, key off.

 

[Bobmbx]

I just feel if it was an electrical issue, I wouldn’t be able to turn on my car one second and it stalls instantly, and then at the next moment, turn on my car a second, third, or fourth time and all the sudden it’s running perfectly.

Welcome to the world of electrical faults. The possibilities are endless. Electrical and electronic systems are designed to run correctly in one configuration. Alter that configuration and the results can be unimaginable.

Radios that cycle on and off when the turn signals are activated, horns that blow when you raise the right rear electric window, interior lights that never shut off, etc....

These kinds of spurious and unrelated faults can result from power being applied where it isn't supposed to be (short or ECM failure), power not being supplied when it is supposed to be (ground or ECM failure), or bad sensors that cause the ECM to issue unneeded commands, like a bad O2 sensor that causes the ECM to lean the fuel that results in a misfire, which immediately causes a new set of plugs and wires to be installed and so on and so forth.

That's why Nate is pushing to stop solving each symptom and look for a common cause.

 

[natenkiki2004]

I liked this big reply Nate. Very thorough.

Think of my little priming solution theory this way.. (don’t mind my comical approach to “fuels”)

If the engine consumes 5 fuels per second, and the fuel pump is supposed to provide 5 fuels per second, it balances out, therefore always having a constant and equal supply of fuel.

If there is a problem in the engine and it’s consuming 6 fuels per second, and the fuel pump is perfect and still pumping 5 fuels per second, eventually, the fuel available for the engine will run out.

Adversely, if the engine is working correctly and consuming 5 fuels per second, but the fuel pump is malfunctioning and pumping 4 pumps per second, once again, the engine’s fuel will soon run out.

If there’s some sort of reservoir at the end of the fuel lines that the fuel pools into, but the fuel pump is malfunctioning and only pumping enough to fill the lines and not that reservoir (while the truck is running), the only solution would be to FORCE it to fill that reservoir.. (i.e. fill it while the engine isn’t consuming fuel at a faster rate than it’s pumping out).

So, you would add fuel, add fuel, add fuel, add fuel, add fuel, and now the reservoir would be full.

However, after a short time of running, the fuel pump wouldn’t have been able to keep up with the engine consumption rate and therefore the reservoir would become empty again.

This all sounds crazy, but this is how I’m imagining it happening in my head. I’m probably wrong but I wanted to explain my crazy thoughts.

You're correct to a certain extent. The fuel pumps and injectors in our engine are overbuilt for typical driving, they are in all vehicles. They are meant to deliver as much fuel as the engine needs at redline plus more. When you drive around at 2,000 RPM, chances are good that only 1/4 of the fuel (possibly less) your pump is pumping is actually getting used. The rest is returned to the tank. The way the fuel system is, you should be able to run the engine under 100% load at redline for as long as you like. Other issues like oiling and overheating will come up but that's unrelated to fuel delivery. There's people on here that use the factory fuel pump & injectors with bored out engines, higher compression ratios and all that. Hell, these injectors we use were also found on 5.0 engines. The fuel system, normally, is under very little load. You'd never be able to run the 4.0L engine hard enough to make the pump not able to keep up with demand, it just won't happen. What WILL happen though is voltage drops, intermittent connections and anything else electrical that alter power to the pump. This will alter the RPM of the pump and thus alter the volume/pressure of the fuel being delivered to the engine. THAT'S what you have to look for. Your engine will never use too many fuels

What you said about the voltage thing and having the IAC plugged in makes complete sense.

But then I would wonder why I can’t unplug the MAF sensor instead to make my car driveable? And why only unplugging the IAC gives me those results??

Cause if it was a case of having a limited supply of voltage to take out, and unplugging the IAC allows more voltage to go into the reserve, that would mean in theory I would be able to keep the IAC plugged in and unplug something that takes up MORE voltage than the IAC and get even better results

and I’m pretty sure the MAF takes up way more voltage than the IAC. Could be wrong about that though.

My theory is likely wrong, if there's something bad with the voltage drivers in the computer, it probably wouldn't even deliver proper voltage to all sensors (like the codes you're getting). I only mentioned that theory because you have to think of these kinds of possibilities on your own. You have to think logically and work out the potential problems and then work through those theories to find out if it pinpoints an actual problem.

I just feel if it was an electrical issue, I wouldn’t be able to turn on my car one second and it stalls instantly, and then at the next moment, turn on my car a second, third, or fourth time and all the sudden it’s running perfectly.

AHHHHHHHHHHHHHHHHHHHHHHHHHHH

Hey so I hope you’re having a good Thursday

You'll find that since you have no idea how the computer actually works (you didn't design it, you don't know how it thinks) and you didn't design the wiring and software and everything else involved... problems don't often make sense and that's why electrical and computer stuff often are difficult to diagnose. A computer acting up may be for any number of reasons, most importantly, it may be acting up in ways you never imagined.

Think back to that ScannerDanner video. That truck had him utterly confused, it kicked his ass. He's a teacher in a school devoted to automotive repair, he's been doing automotive & electrical diagnostics almost as long as I've been alive but it fooled him.

Obviously as you found out, just because the IAC being unplugged makes the engine run better has absolutely no bearing on the actual problem. Why is that? Is the engine running lean and the IAC adding more air make it stall? Is the IAC working correctly but maybe the computer is commanding it to be 100% open? Is there even proper voltage at the IAC? Is the computer even responding? There's a million questions to even ask about one specific thing.

You should stop and look at what you know for sure. How could they be related? Get a baseline. Are you even able to reliably pull codes and run KOER tests now?

As for the whole “guessing” thing…

Well, I can tell you for sure that punching my PDB doesn’t make the fuel pump activate anymore. That means I fixed it lol.

I said “I guess” because I couldn’t believe something as simple as pushing back in a loose relay would make the fuel pump stop activating when you punch it with the key in, key off.

It COULD have been a loose connection but you didn't fix anything. At best, you wrapped electrical tape around a leaking hose. If it truly is a loose connection (it shouldn't be, it's not something that gets plugged & unplugged frequently), then you're probably best to replace the pigtail so it's more reliable.




I know I'm being hard on you and by no means am I a professional mechanic that gets things right 100% of the time. But we all go through this throw-parts-at-it phase. We try to fix things by throwing money and parts at a situation without knowing the true cause and often times without knowing if it truly fixed the issue or just masked it temporarily. Vehicles need to be reliable and safe, far too many people ignore those points and worst case scenario, you can take someones life in the blink of an eye. If this was a hotrod weekend project that you fart around with or a farm truck, I wouldn't be as serious. But it sounds like you're using this as a daily driver and frankly, it's not safe as-is. You need to step up and take this more seriously and start learning, especially hands-on. I applaud your willingness and eagerness to learn but please don't do it by throwing money at the problem while risking safety on the road.

 

[MistahYebba]

Little Update...



New codes too.

125: TP sensor input voltage is less than expected.

556: Fuel pump circuit failure.

Also realized that my "code 57" after 998 on KOER is actually 157. There is no seperator flash for KOER. So it's just a standard MAF code about voltage.