Low to No idle - can start with throttle - Here I go again...

[MrShorty]

I'll see the string of KOEO codes, the the separator flash should happen followed by memory codes. I never get the separator flash. Instead, the code flasher shuts off as if I had flipped the switch back to hold.

Have you tried pulling codes with just a paper clip to verify that the problem is on the truck side?

Getting different problem, depending on PCM installed. CM512. Have you carefully been through the PCM wiring to be sure there are no faults in the main PCM power/ground circuits?

I'm just not sure where to go on this one. We started out looking at the IAC, then ended up thinking the fuel pump circuit had problems, then ended up with the main PCM. Three different PCM's give us three different results. I might go over the 60 pin connector for the PCM and make sure all those pins are in there good, no corrosion, no shorts, no ???.

 

[TedJ]

It's really easy to get discuraged with random problems, especially if you are trying and trying to find them and can't. I think you need to maybe take a big step back and look at your truck's whole electrical system. You seem to be getting lots of random "failures" in different areas, that do not go away with known-good replacements.

I would suspect the PCM too, but you have tried two others. The chances of personally owning three bad PCM's are not that good.

I think you may have some intermittent ground or power supply issue that is affecting the computer and making it go crazy... I would check the battery cables, especially the ground and the power supply to the power distribution box, and the power distribution box itself. 12v power in vehicles can do some very, very weird things if the grounds are messed up because the body of the vehicle is part of the circuit in so many ways.

Also, has it ever had any type of alarm or stereo system installed? Look under the dash for some kind of random wiring rat nest/disaster.

Keep trying, you'll get it.

EDIT: What Mr. Shorty said, he beat me to the post.... I agree 100% with him.

 

[motopsycho650]

The only aftermarket thing installed was a interlock alcohol tester. I was the guy who installed and removed the interlock. That's what I do for a living is deal with CO's DUI people. CO requires an interlock after any DUI. I am well in tune with testing wiring because on most 2006 and newer vehicles, I have to find the needed wires under the hood with a test light. Many times without knowing any wire color info. Older vehicles like this explorer, the interlock is hooked up at the ignition harness under the dash.

The original PCM throws different, random codes. The junk yard PCM won't even do it's self test cycle. The paperclip trick did not work. All 3 ground pins on my PCM harness tested with 0 ohms to multiple different frame grounds that I tried. I really just don't want to waste anymore time on this truck, and that's what electrical problems need, lots of time.

I am done with this truck. I am very mad that I haven't figured out the issue, and honestly, I'm to the point that I don't care anymore. I bought it to avoid a car payment for another year or so. So far I've wasted 1500+ dollars, days of my time, and have not even driven 5000 miles in this truck yet. I'm calling it a bad investment and cutting my losses. I am going to start looking for a newer vehicle.

 

[motopsycho650]

I'm not totally giving up on this truck. I'm just putting it on the back burner for awhile. I'm having leg surgery in March, and simply don't have the time or money to chase a problem like this.

Right now, I'm looking to use my tax money to buy a little POS economy car. Something that moves, and doesn't drink much fuel. As I'm recovering from the surgery, I'll work on trying to look at my exploder more.

I talked to another tech last night who is a friend of the family. He thought the same thing I currently do. It has at least one major electrical problem, if not more. It's probably not that big of a problem, but the issues is the time needed to find it. I can't afford to pay anyone for that kind of time, and currently, I don't have the time myself. I'm sure I'll be back a little later in the spring.

 

[motopsycho650]

It seems fixed now. I did have a bad PCM, and a bad Bank 1 O2 Sensor.

I was reading through TSB's and other forums from work. I found a problem where the O2 Sensor can short out, and actually short that circuit in the PCM.

My cousin borrowed a Snap-On Motis from someone. We hooked it up and looked at the data stream from the PCM. It identified the O2 sensor as being bad. The sensor would stay at minimum voltage for up to 5 minutes, then would flip to max voltage for about 30 seconds. The other O2 sensor looked perfectly fine.

I replaced the O2 Sensor with the junkyard PCM still installed, and it runs like new. I then tried the OE PCM and it was dead again. From what I've found in TSB's, Ford had a much bigger problem with '94 PCM's than previous or later years.

Here's a few things I've learned through this: 1. An O2 sensor code is rarely a bad O2 sensor. 2. If an O2 sensor is pegged on LEAN, the PCM thinks there is a fuel pump delivery problem. 3. If the O2 sensor is pegged on RICH, the PCM thinks there is a Mass Airflow problem. STUPID OBD1 logic...

Now, I really hope it doesn't run for two weeks and die on me again....

 

[Tony H]

I got my fingers crossed .
I hope you got it solved

 

[MrShorty]

And thanks for posting some of the diagnostic details you went through to get to this point. Too often, it seems, people only post what they replaced to fix the problem without explaining how they determined why that was the problem. All too often, as this situation illustrates, diagnosis is 90% of the battle.

 

[TedJ]

And thanks for posting some of the diagnostic details you went through to get to this point. Too often, it seems, people only post what they replaced to fix the problem without explaining how they determined why that was the problem. All too often, as this situation illustrates, diagnosis is 90% of the battle.

^^^ x2

Good Luck, hopefully it will be working now and you can put some happy miles on her...