1992 F150 Lariat XLT 5.0 5 Speed Manual

Hi all! I'm getting some strange codes from my KOEO tests and I figured I'd post them here to see if anyone has any suggestions. The first code that I'm getting is code 67, which seems weird to me since I have a stock manual transmission. Maybe I'm reading the code explanations wrong but it seems that that code deals with automatic transmission problems. The second code that I'm getting is 1294. The CEL flashes once, then twice, then nine times, then four times. Then repeats the sequence again. The problem is that there is no 1294 code listed on the Ford OBD1 code list. I've done the KOEO test three times now and these are the codes that I'm getting. Am I just not looking in the right place or is my truck going through an identity crisis?

The reason that I'm performing the tests is that the CEL comes on after about 15 minutes of driving. I was hoping that the CEL would point me toward why the truck is hiccuping under steady loads. Sometimes it's barely noticeable, other times you can definitely feel it.

Any help figuring out what I'm doing wrong with the OBD1 codes will be appreciated.

 

I'm looking at the 1993 PCED manual right now. A code 67 can apply to the MLP sensor or the Park/Neutral Position sensor. It'll also trigger if the AC is on during the test. I would not expect this code to cause a driveability concern.
Ford EEC-IV controllers did not have 4 digit codes. I initial thought you were seeing a separate pulse with a code 294, but there is no code 294 listed as well so I'm a little stumped there.
It's been a long time since I've had to jumper and count pulses since I bought an NGS off of eBay long ago to make my life easier.

As for the symptoms, can you describe it a little more? Does it feel like you're momentarily losing power, then it comes back? Anecdotally, I had symptoms like that on my 1996 F350, I wasn't losing fuel, but I was losing the electronic spark advance, which reverts it back to base timing set by the distributor instead of the electronically controlled additional spark advance commanded by the PCM. I ended up tracing it back to a corroded connector at the O2 sensor causing an intermittent open circuit condition. I was not getting a MiL to light up in that instance.

 

I own a NGS too
Agree
Have the codes read by a machine
You can pick up a super star, or a super star 2 pretty cheap these days
Should be 3-digit codes on that OBD1 '96 F350

 

For some reason the OBD1 port in my truck will not connect to a reader. I bought one years ago and never could get it to work with my truck. Ditto for the shops that I have taken her to that have tried to use OBD1 readers on her. A KOEO test has been the only test that I have been able to run for several years, unfortunately.

 

When I'm driving at steady speed every few seconds I feel a momentary loss of power, almost like I'm tapping the brakes for a split second. It happens randomly, 5 seconds apart, 60 seconds apart, 30 seconds apart, etc. It's strong enough for me and the passenger to feel, but not as strong as what I would call "bucking", if that makes sense. To make it even more annoying, it isn't consistent. It's much more pronounced on some drives than others.

And as I told ManicMechanic007, the OBD1 reader port in my truck hasn't worked for many years, since at least 2015. Not for me and the reader I bought, or for the shops that I have taken the truck to for repair. So unfortunately I'm stuck with reading flashes.

 

Can you try to clear the codes in active memory and then drive until they come back? Also, when you run the KOEO test, make sure the AC is off to see if the code 67 comes back. If it does come back, work to check out that circuit first just to clear things off the table. This is going to seem like a weird request, but could you also disconnect the AC clutch at the compressor and leave it disconnected for awhile? There is a WOT AC cutout feature and if the truck thinks it's going to full throttle intermittently, the AC will cycle on/off. I wouldn't expect to be very noticeable to passengers, but the as the driver you'll feel it cycling. If the symptoms persist with that disconnected, feel free to reconnect.

Do you have wiring diagrams and the ability to pinpoint test the harness? Or even, perchance, a breakout box for EEC-IV? Unfortunately there are a lot of thing that could cause the symptoms you're feeling and without a code (that makes sense) to point us in the right direction or a continuous fault, it's going to be a project to diagnose. What you're feeling could be a interruption in spark, spark advance, fueling, or a reversion to backup controls. All of those things, and more, will feel like a sudden shift in control strategy leading to a momentary loss of power.

I went through this on my Bronco, it would just shut off then instantly come back on while driving. It usually was not "momentary", if the engine did come back on it was several seconds later. That turned out to be a bad MAP sensor. I had that harness torn apart, I had the breakout box sitting under the hood, and I had an oscilloscope teed into my map sensor signal lines. BTW, the MAP sensor on these trucks is a little computer all on it's own, it takes in manifold air pressure to and outputs a digital signal with a frequency corresponding to pressure. Not easy to measure with a standard multimeter unless it has that capability.

Things I would start with; some of these you may have already done.
- Check all grounds under the hood, look for broken wires and corrosion, clean and repair as necessary
- Generally inspect harness through engine compartment and look for obvious damage (corrosion in connectors, rodent chewed wires, etc)
- Check fuel pressure, make sure fuel pressure holds with the engine off, check vacuum line going to fuel pressure regulator, it should be dry (no fuel in it) and not be aged/cracked
- Check spark plugs to look for obvious cylinder to cylinder differences. Inspect distributor cap and rotor for wear.
- Check condition of vacuum lines in general, these trucks used plastic formed vacuum lines which can become brittle over time
- Check operation and expected voltage range of the Throttle Position Sensor, slowly sweep it and look for discontinuities on the multimeter, then make sure the the voltage is within range specified at the end stops
- Inspect TFI module to make sure it's not burnt or distorted from heat. This may be on either the fender or the front of the distributor.
- Inspect harness down to O2 sensor for damage.
- If you find nothing in the above steps, I'm afraid the next steps are a harness pinout and shake test or a parts cannon...

I don't normally advocate for the "parts cannon" approach but I have done it in the past out of sheer frustration. If you do replace components, try to buy only Motorcraft, especially for the MAP sensor and TFI module. For O2 sensors, I stick with Motorcraft or Bosch, but the OEM one is likely Bosch or Denso, which you can also buy those brands directly.

 

Thanks for all of the suggestions krugford, I will get started on working through the list of things that you've suggested today and I will post any and all results in a day or two. In the meantime, the radiator on the truck decided to take a dirt nap yesterday so today's project will be radiator and hose replacement.

 

A quick search reveals nearly all OBD1 codes were 2 digit.

code 12 - unable to control idle rpm
code 94 - A.I.R system inoperative


https://www.troublecodes.net/ford/aerostar-vanwagon-bronco-econolineclub-wagon-explorer-f-series-ranger-1992-1997/

 

That was my thought too initially, but there is no gap between codes. When I got the first code, 67, there was a gap of about 7 or 8 seconds and then the CEL flashed 1294 in quick succession with no gaps at all. I have a list of two and three digit Ford OBD codes, but there are no four digit codes so my initial thought was that maybe the single flash was meant as a divider, but there is no 294 in the three digit code list.

 

Do the 2 digit codes fit your situation, I.E. current idle control and a.i.r. condition?

If it was never designed to deliver a 4 digit code than you have to assume it displayed two 2 digit codes. You will never find a description for a 1294 "code".

The "gap" between codes may be much smaller than you were expecting or interpreted, or it took the system those 6-8 seconds to indentify the last 2 of the 3 codes.

Computing in general was much slower in '92.