Electrical 1993 lx 5.0 code 18 issue

mondos90lx

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So after roughly 12-13 years I bought another Mustang and I need some help. I bought this 93 Mustang last September and am just getting it on the road now. I replaced the several items because it was running funny with a hesitation between 1400-2000 RPM. I replaced the IAC, EGR, TPS, fuel filter, cap, rotor, plugs, wires, and coil. The MAF was a C&L unit calibrated for 30# injectors and not the stock 19# which are on there so I replaced it with a Pro-M calibrated for 19# injectors. Just small stuff.

Well when I was putting the battery back in I reversed polarity and got a quick spark. Car then would crank but not start. Went through the crank but no start online checklist, checked all the fusible links, swapped out the coil, cap, rotor, stator, and wires with OEM ones, installed new ignition switch, and had no luck. Pulled codes and got just got 11.

My buddy who is a ford mechanic then came over and went through it all, cleaned the new plugs, put everything back together and it started up and ran nice then died. Pulled the spout connector and it started up again. Replaced the TFI module and it worked. Drove it around the neighborhood a few times and no issue.

Got it registered today and came home, let it run for a few minutes then it died again. Pulled the spout and it started fine. Replaced the distributor with a rebuilt OEM one, set timing and it ran fine. Installed the spout in and it ran fine. Took it down the street and it felt good, ran it through the gears, Street is about a mile long. Coming up to a stop sign, I throw in the clutch and it bogged down and lost power. Idling under 500 RPMs. No throttle response pretty much out of nowhere. Pulled the spout and power came back and i coasted back home. Checked codes and got a code 18 which is the spout. Replaced the autozone TFI with a Ford motorcraft one (brand new), didn’t help, car still threw a code 18.

I then checked continuity in the circuits from the TFI connector down to the ECM connector at pin 4 and 36 and both had the correct ohms (I attached the picture below from a stangnet thread). So I swapped out the A3M ECM to a known good A9L. No luck, still throwing a code 18 and the car will only turn on with the spout removed. With it removed it idles and runs fine. TPS is set. Timing is set at 10 degrees. Not sure what it can be. It’s getting fuel, fuel pump runs (I accidentally flooded the engine and had to replace the oil and filter and cleaned off the new plugs), and it’s getting spark.

Motor is a 306 with Edelbrock performer heads, E-Cam, cobra intake, 70mm TB, stock injectors, adjustable fuel pressure regulator, electric fan, CAI, full exhaust, and that’s about it.
 

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jrichker

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Probable TFI or PIP sensor problem...

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.

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.

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).





Resistor location: A big thanks to liljoe07 for this information:



Check over by the brake booster. Its not in the harness on the TFI, its on the main part of the harness over by the plugs that connect to the dash harness. About 6" or so from that, going back toward the EEC.



If I remember right, the resistor is covered in a shrink tubing that is sealed to the wires. So, you wont be able see any markings. The shrink tubing is labeled though. It's a 22kohm 1/2 watt resistor.



Here is the location.



attachments\532446




Next measure the resistance between the yellow/lt green wire on the TFI module connector and Pin 36 on the computer connector. With the SPOUT plug in place, you should see less than 2 ohms.



The following is a view from the computer side of the computer connector.

eec-iv-computer-connector-for-5-0-mustang-gif.gif



This diagram is the wire side of the computer connector.

a9x-series-computer-connector-wire-side-view-gif.gif




Diagram courtesy of Tmoss & Stang&2birds



88-91_5.0_EEC_Wiring_Diagram.gif






[b]Code 14[/b] - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.



Revised 8-Apr-2017 to correct SPOUT problem symptoms wording



The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.



PIP Sensor functionality, testing and replacement:[/b]

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.



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%.

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.

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.

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.

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

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.

If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.



The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange



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 [B]http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf[/B] and [B]http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf[/B] for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.
 
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mondos90lx

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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.


So that is between the wire coming from the spout connector into the TFI connector and checking that to ground?

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%.


Got 21,500 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.

.3 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.


.3 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.


.3 ohms
 

mondos90lx

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So at this point I’m thinking it’s a bad PIP sensor. I replaced my old Ford Distributor with a remanufactured cardone one earlier this week. Think the pip can be bad right out of the box?
 

jrichker

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So at this point I’m thinking it’s a bad PIP sensor. I replaced my old Ford Distributor with a remanufactured cardone one earlier this week. Think the pip can be bad right out of the box?
That certainly can happen, the reman distributors may still have the original PIP sensor that they were built with..
 

mondos90lx

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That certainly can happen, the reman distributors may still have the original PIP sensor that they were built with..

Would you be concerned with the 11.68 volts from the red/green wire?

“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.”

What would cause the PIP signal level to drop from the required 6.5 volts? I got .3 ohms on when I checked the pip wiring back to the ECM.
 

jrichker

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Would you be concerned with the 11.68 volts from the red/green wire?

“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.”

What would cause the PIP signal level to drop from the required 6.5 volts? I got .3 ohms on when I checked the pip wiring back to the ECM.
The 11.68 volts should be close enough to work OK.

Heat and time will cause the PIP output voltage to decrease. The remanufacturing process means that they only fix what is obviously broken. The may not do an actual output test on the PIP sensor voltage.
 

mondos90lx

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The 11.68 volts should be close enough to work OK.

Heat and time will cause the PIP output voltage to decrease. The remanufacturing process means that they only fix what is obviously broken. The may not do an actual output test on the PIP sensor voltage.

Ok, and is this procedure a valid way to check if the TFI module is working?
 

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jrichker

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@[U]mondos90lx[/U]
Resistance tests on a digital semiconductor device isn't a reliable method of finding good or bad components. It will find short circuits or open circuits, but does not give any useful information about if or how well a device functions.
 

DOHCobra

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I have an very similar situation with my 93 LX 5.0 5spd. Last weekend 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. Last owner had the car for 15 years and was maintenance oriented and not a big hot rodder. 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 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, since I planned to replace them soon for peace of mind I thought I would start there. A week later 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 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.

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. What is the purpose of the 100K ohm reference point? I have infinite ohms, open circuit, on ohm meter which is greater than 100K ohms but I struggle with this test. Below in next steps for PIP I measure the resistance of this wire between the TFI and computer connecter ends and it is 0.2 ohms. I don't understand how measuring the resistance of a loose wire with no resistance and ground would result in a reading other than infinite open circuit unless it was grounded itself and would measure 0 ohms. Let me know if I am missing something here. Guessing open circuit good, shorted circuit bad.

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. 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. Definitely not 12-13 volts. What should I be looking at next? Another internet reference suggested 8-10 volts is acceptable result for this test.

Last observation to share is that I put the connectors back on TFI and computer, started the car again without SPOUT, no change and not expecting any, but this time I moved, wiggled, the wire harness at the TFI connector and found the engine idle was affected slightly when wires were moved. Should this happen? I then went to the firewall end of this harness and moved it again with no effect on engine idle.

Also adding a picture of my TFI connector and wiring colors. My wire colors are different than those in the schematic above, only the Red/Blue and Red/Green are similar. Though the position of wires seems to be functionally the same when troubleshooting. Thought maybe just age faded colors, but the colors are consistent throughout the harness. ???

Still reads a Code 18. Appreciate any ideas on next steps in troubleshooting.
 

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