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1993 Explorer XL loses power when driving

PStansberry78

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Hello All - First time poster.

I recently acquired a 1993 Explorer XL, 4.0L OHV, 5-speed manual transmission. It's well-used, LOL, but overall seems to be in reasonable shape for it's age.

But, it has a problem I can't seem to figure out. Inconsistently (I can't establish a pattern), it will suddenly lose power while driving. As you push on the accelerator, the RPMs will increase and then suddenly drop when it hits around 2000RPM. But it occurs often enough to make it unreliable as a daily-driver, unfortunately.

Also, the check engine light will sporadically flash on for a bit, then off again as this problem occurs.

I'm hopeful you all can help point me in the right direction. After spending some time Googling the problem and looking here on the forum at similar threads, I suspected that it was a fuel delivery issue of some sort, as it also smells as if it is running rich when this issue occurs. So my trouble-shooting to date has centered around the fuel system, mostly.

Here's what's been done already:

  • Fuel filter replaced
  • Fuel system flushed/cleaned
  • Fuel pressure regulator replaced
  • Ignition Coil replaced

I'm now wondering if perhaps the throttle position sensor could be part of the problem? I'll be the first to admit that I'm only a fair shade-tree mechanic, and by no means an expert. So any advice would be helpful.

Thanks in advance.
Paul
 
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4x4junkie

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Welcome to the forum :chug:

Have you pulled the codes for it yet? (with the CEL having come on, there should be at least one stored code)


FWIW, I had something similar on my '94 4.0 Ranger (would sporadically lose power, run rich and guzzle fuel while the CEL would come on & go off, though it never threatened to fully stall or anything). A high load on the engine is what triggered it (towing, driving up a grade, etc.). Codes were all over the place (lean on bank-1, lean on bank-2, rich on bank-1, rich on bank-2, MAF out of range, and I think one other I can't recall). Turned out to be fouled O2 sensors apparently brought about by use of a K&N air filter (which I since got rid of).

If you haven't pulled any codes yet, I would suggest you do so before you go any further yet.

How to pull codes

Hope that helps
 
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PStansberry78

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Thanks, Junkie - I haven't pulled codes yet, because I didn't realize there was a way to do it without a reader. I'll work on that tonight and see if I can get anything useful out of the computer.

O2 sensors are something I hadn't considered yet. Thanks for the tip.

Paul
 
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PStansberry78

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OK - If I did this right, my results are:

KOEO: 111 (clear)
CM: 512 (Memory error???)
KOER: 137 (O2 sensor not switching/system rich left or front HO2S)

I'm looking through my Haynes manual and I can't seem to locate where the O2 sensor(s?) is/are. Looking the part up, it seems like a cheap part. Is it simple to replace it?

Paul
 
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PStansberry78

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OK - I think I've located these on the exhaust manifolds underneath. There are two of them, but what I can't tell is whether it's the same part on both sides? Even though the CEL code was only for the driver's side, is it worth just replacing both at the same time for good measure?

The part is only $27 on Amazon.

http://smile.amazon.com/dp/B000BZG8ZA

Paul
 
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FR-425

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Hold on a second!

Before you start throwing parts at it.

Disconnect the battery for two minutes to clear the codes.

Reconnect and pull the codes again.

My guess is that you will still get the 512. (and others)

If you consistently get 512; the PCM is bad and will need to be replaced before you can continue to trouble shoot.

512 is Failed Keep Alive Memory test. The KAM is not just used to store fault codes, if the KAM has a permanent fail (repeat 512) it's toast.

The KAM is used for "live" data while driving, this can cause all manner of performance issues and false fault codes, depending on which memory block is bad.

Each data type is written to the same memory address every time. So a KAM fail can effect any system at random.

It stores data on the last drive cycle after shutdown, as well as "live" fuel injection timing data while in drive cycle, "live" ignition timing data, engine rpm, etc.



512 and 513 are known as "Death codes"

Do the "clear and retest several times" if you get the 512 again it's time to start looking for a PCM.
 
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PStansberry78

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Hi FR-425 - Thanks for the details! I'm learning a lot here.

I'll go run the code tests again and see what I get. Do I actually need to disconnect the battery or is resetting via the jumper acceptable?

Also, what exactly IS the PCM? I see PCM and ECM. What's the difference?

Paul
 
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PStansberry78

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OK - I see your point. I just ran them again and it's still throwing the CM 512 and the KOER 137 and now a KOER 116 as well. I've pulled the neg and will run them again after that sits for awhile, too.

Is the PCM difficult to replace?
 
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PStansberry78

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With more reading, it looks to me as if PCM (Powertrain Control Module) and ECM (Engine Control Module) are NOT the same. Is that correct?

Paul
 
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4x4junkie

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I can confirm a code #512 generally = PCM replacement.

PCM = Powertrain Control Module
ECM = Engine Control Module

The two terms are often used interchangeably, however Ford uses "PCM" in their service literature.

I would try a junkyard or Ebay first for a PCM. You'll need to match it's part number digit-for-digit though, they generally are not interchangeable between model years, auto vs. stick, and Calif vs. Federal emissions.
IIRC, the PCM is located behind the passengerside kick panel on the Explorer.


Edit:

Hold up up on the #512 thing... Now that I think of it, there may be a separate electrical circuit that maintains the PCM memory, which if disconnected might trigger the code. Lemme look at a schematic for a sec...
 
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4x4junkie

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'k, I'm looking at a diagram (along with the powertrain/emissions diagnostic book), and I see pin #1 of the PCM is a "Keep Alive Power Input" (plain yellow wire, no stripe). This wire should always have a constant 12V on it. If that wire infact has 12V on it at the PCM, then replace the PCM. If the wire has no voltage (or is less than 10V), then you'll need to check for a blown fuse and/or repair that circuit somewhere it is damaged.
Looks like the fuse for it is in the power distribution box under the hood.

Hope that helps
 
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PStansberry78

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Well - I checked the fuses in the power distribution box because that was something I could do quickly. Nothing obvious there, so I'll have to dig into the voltage stuff over the weekend.

You guys have been great. Thanks so much for all your help!

Paul
 
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larrydd999

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Paul, I have one other suggestion - if you're checking the codes with anything but an LCD type code reader, you're working too hard! I purchased my code reader a couple of years ago (replacing a much older blinking LED type) at an auto store for about $35 and it's paid for itself many times. Of course, the fact that we have 4 Fords that can use it did influence my decision... That and a decent digital multi-meter (DMM) have saved me a lot of time and money over the years.
 
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FR-425

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RockAuto is gonna be your best bet on a replacement PCM

http://www.rockauto.com/

Make sure you have the thing in your hand, so you can read the full part number and call them to verify over the phone that they have the right one.
 
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PStansberry78

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OK. My local O'Reillys has one they can pull from their warehouse tomorrow. Is there any reason not to use one of these Cardone remanufactured units?

Remanufactured PCM

Looks pretty plug and play... And for $109 that's a more attractive part than a new one.

Paul

Edit: Turns out Autozone has one on hand. I'm off to pick it up shortly. Old one is out already.
 
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FR-425

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No Cardone has been around for ever.

Their reman will hold up.

When you get it in your hands, just verify the part number and the "BIG" letter code for a match.

This will make sense if you are looking at the unit.

You do have it out yes?
 
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FR-425

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And yes it will be "plug and play"

Just unplug the old (battery disconnected of course) and plug in the new. Done!
 
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PStansberry78

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No Cardone has been around for ever.

Their reman will hold up.

When you get it in your hands, just verify the part number and the "BIG" letter code for a match.

This will make sense if you are looking at the unit.

You do have it out yes?

Yeah - It's out. Pulled the battery connector, then just unbolted the mount and then unbolted the connector. By "BIG" numbers, I'm assuming you mean the ANY1 in this pic? What are those numbers? I've only been seeing references to the F37F-12A650-YB number as I've been looking up parts online.

WP_20140430_19_54_25_Pro.jpg


Paul
 
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FR-425

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Yep those be the "BIG" numbers.

Those designate; Federal or California emissions; auto trans or manual; ignition type; injection type; all that raz-ma-jaz.

Plus the base Ford part number, all add up to the specifics of the truck.

for example; some 93's have batch fire injection and others have sequential.

Put the wrong PCM in there and - no go -

ALL those numbers need to match.

You can see the injection designator; EFI-MA46G

I believe the YB at the end of the Ford number is for "Manual trans Base model", so I'm guessing it is 2wd, if I remember the code right.

But you get the drift... .. .
 
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