Electrical 93 5.0 LX Code 18 SPOUT in Issues

DOHCobra

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Sep 16, 2018
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New to forum and think I have read most posts referencing a Code 18 and SPOUT issues. My trouble shooting results are slightly different from the other posts I have read so sharing to get some insight for next step in solving my problem.

I have a 93 LX 5.0 5spd convertible. Two weeks ago took it out as usual except it took three attempts to start vs the usual start on first try. 1.5 miles down the road, pull it out of gear approaching a stop and the idle drops, stumbles and engine dies. Would not restart within an hour, towed it home and checked for codes. Code 18 is only code that came up. I started scouring forums and internet for some Code 18 wisdom. Found a lot of information here, but not a perfect fit or fix for my situation yet.

I have owned the car for only four months so I have inherited a lot of unknown history. It is 60k miles, relatively stock with exception of last owner adding a Vortech and not much else. The owner prior to him installed a 5spd in place of automatic and a 3.55 rear in place of 2.80 all done with factory OEM parts, no aftermarket or performance pieces to be found. The computer is an F3ZF-FA so appears to be correct for current set up

The fuel pump primes with key on and has pressure, but I have not measured it with gauge yet. My coil and distributor/TFI appeared to be factory original Motorcraft. I planned to replace them soon for peace of mind so thought I would start there. First I attempted to start the car without any changes. It fired up with SPOUT in and ran rough, eventually stalled. I swapped out the coil and again it started up and ran rough, eventually stalled. I then swapped the distributor for a new unit (not remanufactured) with new TFI and again it started (SPOUT out to set timing) 10BTDC, it ran rough like the original distributor, no change. I put the SPOUT in and the engine stalled almost immediately. I checked the timing when I first got the car and it was at 10BTDC and the SPOUT did advance the timing 4 degrees when installed.

I then began following the Code 18 troubleshooting logic from this forum and will add my results and questions in the copy paste of the procedure below for reference.

Code 18 - SPOUT out or wiring fault - look for short to ground in SPOUT wiring going back to the computer. Possible bad TFI or defective 22 K resistor in the IDM wiring

Use a timing light to check the timing: remove the SPOUT and observe that the timing retards at least 4 degrees. Put the SPOUT back in place and observe that the spark advances at least 4 degrees. Timing at 10BTDC with or without the SPOUT, no timing change removing spout. I noticed that when handling the spout pigtail that the engine rpm did vary noticeably. I found the SPOUT was loose and not continuously connected. I disassembled the spout plug, bent the tangs of the female connectors to better engage the SPOUT blades. SPOUT now plugs firmly in place with continuous contact. Still no SPOUT effect on timing. Engine struggled to run with SPOUT in and does not start with SPOUT in. After fixing SPOUT plug, I still noticed changes in engine running when handling the TFI harness near the plug, not as bad as loose SPOUT but noticeable. I soldered in a new TFI connector and this fixed the variations upon handling the harness. Checked to see if code 18 went away - still there. Ran car, would not start with SPOUT in, no change.

This code can disable spark advance and reduce power and fuel economy.

Remove the passenger side kick panel and disconnect the computer connector.

There is a 10 MM bolt that holds it in place.

Disconnect the TFI module connector from the TFI and the measure the resistance between the yellow/lt green wire and ground.

You should see greater than 100 K (100000) ohms. I have infinite resistance or open circuit, so greater than 100K ohms

Check the resistance from Pin 4 on the computer connector (dark green/yellow) and the dark green/yellow wire on the TFI connector. You should see 20-24 K Ohms (20,000-24,0000 ohms).
21.8K ohms

PIP Sensor functionality, testing
Some simple checks to do before replacing the PIP sensor or distributor:

You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.

Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.

Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
21.8K ohms

Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
0.2 ohms

Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
0.2 ohms

Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
0.2 ohms

Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Steady 12.0 V

Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
10.0 volts while cranking. Definitely not 12-13 volts. What is the corrective action for this condition?

Thanks,
 
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jrichker

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When cranking the engine, it would not be unusual to see the voltage drop off to 10 volts.

PIP problems & diagnostic info
Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.
 

DOHCobra

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Sep 16, 2018
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Good article has me thinking. I do not have and oscilloscope or GMM to measure PIP signal and voltage, may have to invest or get to a shop that does. Appears the article issue was that they had spark but not fuel due to weak PIP sensor issue when hot.

I tested injector pulse with NOID light and I do have injector pulse with SPOUT connector in and out.

I also used an inductive timing light on coil wire to distributor. Coil fires with SPOUT connector out while cranking and coil does not fire with SPOUT connector in while cranking.

So I have fuel but no spark with SPOUT connector in. Has me thinking that when I connect SPOUT to computer the code 18 issue that the computer diagnostics is identifying is within the computer.

Any issues with my logic? Other thoughts?

Thanks,
 

jrichker

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Good article has me thinking. I do not have and oscilloscope or GMM to measure PIP signal and voltage, may have to invest or get to a shop that does. Appears the article issue was that they had spark but not fuel due to weak PIP sensor issue when hot.

I tested injector pulse with NOID light and I do have injector pulse with SPOUT connector in and out.

I also used an inductive timing light on coil wire to distributor. Coil fires with SPOUT connector out while cranking and coil does not fire with SPOUT connector in while cranking.

So I have fuel but no spark with SPOUT connector in. Has me thinking that when I connect SPOUT to computer the code 18 issue that the computer diagnostics is identifying is within the computer.

Any issues with my logic? Other thoughts?

Thanks,
It is possible, but it is also an expensive guess...
 

DOHCobra

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More an inferred diagnosis based on troubleshooting observations and results than a guess. I found an ECM rebuilder who will diagnose my unit before performing any rebuild service. I will update in a week or so after I get my ECM diagnosis and refreshed unit back.
 

DOHCobra

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Sep 16, 2018
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NE Wisconsin
ECM came back early this week from EcuExchange in Florida. Power supply, capacitors and voltage regulators updated. Engine fired right up with SPOUT connector in, which it would not do previously. Ran fine for a short while, sounds more synchronous than it did before, but still have the coil misfire symptom as before, less with SPOUT connector out, but it continues to drop coil fire erratically. Still get Code 18.

Went back to the Code 18 troubleshooting steps.
  • Opened the TFI harness wiring back to the firewall, shielding was good, wiring looked to be in pristine condition so stopped there and rewrapped it. Resistances were all OK.
  • Since I now have two TFIs took them to Advance for testing. The original Motorcraft failed first test cycle, and passed next two. The new TFI that came with replacement distributor passed all three test cycles. The new TFI is noticeably heavier than the original - probably has more heat sink material. Reinstalled the new TFI.
  • Still looking for answers I studied the wiring diagrams, particularly related to the coil negative side of circuit and thought of checking the 22k ohm resistor again. The IDM wire from TFI harness to ECM connector showed 22k ohm. I unwrapped the resistor from the harness, cut it out and measured resistance at 22k ohm when it was stationary. I shook the resistor with the ohm meter connected and the resistance varied +/- 10-20k ohm. I then flexed it slightly and the resistance swung from zero to infinity and everything in between. I soldered in a new resistor and it is rock solid 21.7k ohm now.
Fired engine and although the tach is more steady when coil misfires, the coil continues to misfire.

Issues corrected to date:
  1. Replacement distributor and coil had no effect on coil dropping fire, but I did find that the original distributor has noticeable rotational resistance in the shaft bearings compared to free spinning new distributor
  2. SPOUT connector plug was loose and SPOUT was not always electrically connected as found in wiggle test, fixed by adjusting female connectors of SPOUT harness plug
  3. TFI harness plug also showed some variation upon wiggle test - replaced plug, now solid connection
  4. Computer had some weaknesses and parts beyond expected service life, but not likely the root cause of my problem
  5. IDM circuit resistor had big issues - replaced it.
I plan to have a closer look at the PIP sensor signal of both the new and original distributors. Open to other thoughts on the Code 18 troubleshooting and potential next steps.
 

jrichker

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A other thought: do any of the other accessories - radio, heater, turn signals have problems at the same time the engine misses? If so the ignition switch and associated wiring are suspect.


It seems that you have had an unusual number of loose connections and wiring problems. I would swap the ignition
coil around one more time with one of the spares you think may be good and while you are at it, check the ignition
coil connections.
There is a fuse link in the wiring that feeds the ignition coil and It may also have some connection problems,

The following are diagrams courtesy of Tmoss & Stang&2birds

Fuel, alternator, A/C and ignition wiring
fuel-alt-links-ign-ac.gif


Ignition switch wiring
IgnitionSwitchWiring.gif


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.


TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
 

DOHCobra

Member
Sep 16, 2018
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4
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NE Wisconsin
Thanks for the thoughts and info jrichker. Agree there is an unusual number of electrical connection issues. Feels like I have eliminated the usual Code 18 problems by replacing a bad resistor in IDM, and determining the SPOUT wire is not grounding out and its resistance is 0.2 ohms.

I have run accessories and they are unaffected when coil misses and engine stumbles. I looked at the ignition switch - it appears solid, no separation or looseness, and it provides continuous battery voltage to TFI on Start and Run key settings (checked with test light and volt meter).

Tested the coil positive lead with a test light and the light is solid on when coil cuts out/engine stumbles, coil seems to be getting uninterrupted positive current. Put the test light on the negative side of coil and it is blinks on when the coil grounds to fire, and the test light is off when coil misses/engine stumbles. To me this is suggesting the coil is not getting a ground signal to fire from distributor or TFI. Even does this with SPOUT connector out and no computer input. This has me wanting to look more at the distributor, PIP and TFI. I do have the new distributor in, but doesn't rule out it might also have issues.

I have battery voltage at ground to engine block/distributor housing when the engine is off. For fun I plan to run a jumper from battery negative to engine block to rule out a bad engine ground wire that only shows up when engine is running (ignition is grounded to the distributor, might explain the random cut out).

That is all I got, will update once I get some additional information to share.
 

DOHCobra

Member
Sep 16, 2018
16
4
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58
NE Wisconsin
My ground to engine block was solid with the engine running, not an issue.

I kinda broke a trouble shooting rule by changing parts and not returning to the original parts if the new pieces did not fix the issue - specifically I left the new distributor and TFI in the engine when they did not fix the issue when first installed, thinking a new distributor/TFI is better than potentially 25 year old parts.

Problem Solved!

Long story short, after all the corrective measure mentioned previously, I put my original Motorcraft distributor and TFI back in the engine and the Code 18 was eliminated. It appears the root cause of my problem was a faulty IDM resistor, further complicated by a bad TFI associated with the new distributor assembly.

In the end I reinstalled the new distributor with the original Motorcraft TFI and all is good.

Thanks for the help and suggestions.
 
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