Warning: Tfi Control Module Monkey Business

Mar 7, 2016
148
9
28
Woodbridge, VA
#1
Hey Gang,

I have been chasing an ignition problem for quite some time now, and I'd like to share my experience buying new TFI modules as a cautionary tale for those who may be in the market for one.

I had my original module tested at Autozone, and it passed. For gits and shiggles, I also did some "rough" resistance tests on it too, which confirmed Autozone passing result. (Note that "rough" resistance tests were only to make sure that there was resistance on pins that should have ohms and no resistance on pins that should have 0 ohms. These are the only meaningful resistance tests to be performed when bench testing the module itself--the ohm values aren't so important--it's GO/NO-GO. Same idea as when checking resistance on capacitors that are wired into a circuit board; only infinite or 0 resistance results are meaningful.)
See:
http://www.myo-p.com/Ford-EEC/EEC Help files/Files/TFI test and troubleshooting.html
for a diagram showing which pins should have SOME resistance an which should have none.

Anyway, my original unit tested fine both ways, but i ordered another one so as to have a spare on hand as i understand that our cars are notorious for burning through these things. Here's where the debacle begins..

1. Ordered OE replacement unit from LMR and bench tested it straight out of the box. Sure enough, the GO/NO-GO resistances were all jacked up. It was clear that one particular pin had an internal break. It had OL ohms across the board. Took to Autozone: fail confirmed. Called LMR and was able to convince the guy that it was DOA and to give me a refund w/o being on the hook for return shipping, although, it did take some doin'. He surely would not have been so "understanding" had i installed the unit--he asked about this twice. Guy also asked if i got receipt from Autozone confirming fail (Note: Autozone provides no such receipt and clerk will look at you funny for asking). I am grateful to have received refund.

2. Ordered Motorcraft unit from RockAuto. Second verse same as the first. Failed bench test and Autozone test (this time i snapped a pic of the unit failing on Autozone's machine.. My "receipt of failure" in case RockAuto asked). The refund/exchange process with RockAuto was much easier. However, i noted that my Motorcraft unit curiously had no Motorcraft/Ford logo like my old one. According to Ford Motorcraft website's FAQ,
How do I know if a part is counterfeit?
"Unfortunately, our high quality breeds a lot of imitation. Every Ford Part is stamped with the Blue Oval or Motorcraft® brand so that you know it’s authentic. If a part you received does not have one of those stamps, then it’s not a Ford Part."
I contacted Ford Motorcraft with pics and they said it was legit despite no branding and that my beef was with RockAuto seeins how they sold me a broken part. Weird, considering what their website says, but okay. Initiated RockAuto exchange, no problem.

3. Received second unbranded Motorcraft module; same outcome as before! Failed both tests. Now i will initiate a refund because i am tired of bench testing new parts and running to Autozone all the friggen time (however, i now know how to use their ignition testing equipment better than many of their associates :nice:).

In summary, watch out. Be sure to have your new TFI modules tested prior to installing them. Vendors are inclined not to accept returns on these parts--Motorcraft units included--if they've been installed. Also, take pics of the failing test result should vendor ask for a "receipt of failure."

I have no idea what's going on with brand new TFI modules these days. I have pulled myself out of the market for the time being as my original unit--the one that SAYS Motorcraft--is still serviceable. I hope this post is not too rambling and incoherent, and i hope it proves useful to some of y'all.:flag:
 
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stpete

Active Member
Dec 26, 2015
324
158
53
52
#2
I had problems also. I bought the PDI Dyna Mod module hoping it would be better than standard. Nope. Got two bad in a row. I didn't test them on a tester, but there was a miss in the car as soon as the starter caught and they burned themselves up within a small amount of time. I got a new Motorcraft (from Amazon I think) and it works well. I think my idle is slightly better than with my original motorcraft TFI. That one is now my spare. Everything I need to change it is in the glove box. One of the PDI modules left me stranded.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#3
I had problems also. I bought the PDI Dyna Mod module hoping it would be better than standard. Nope. Got two bad in a row. I didn't test them on a tester, but there was a miss in the car as soon as the starter caught and they burned themselves up within a small amount of time. I got a new Motorcraft (from Amazon I think) and it works well. I think my idle is slightly better than with my original motorcraft TFI. That one is now my spare. Everything I need to change it is in the glove box. One of the PDI modules left me stranded.
Guess i'm not the only one. Sorry to hear you got burned. The Motorcraft unit you got that worked out, was it one that has Motorcraft logo or one of the blank "we-swear-it's-a-Motorcraft" ones?
 

jAEded

Active Member
Aug 12, 2013
418
26
39
Cali
#4
I have had nothing but problems with tfi modules from local auto parts stores. I haven't tried to find a genuine Motorcraft one yet. I should. The only one that has been working decent is the one that came on my aftermarket tfi distributor.
 

stpete

Active Member
Dec 26, 2015
324
158
53
52
#5
Guess i'm not the only one. Sorry to hear you got burned. The Motorcraft unit you got that worked out, was it one that has Motorcraft logo or one of the blank "we-swear-it's-a-Motorcraft" ones?
It does not have the big block letters like the old one.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
26,665
2,406
224
73
Dublin GA
#6
1.)Was the TFI you received a gray or black one? The gray and black are indicators of some internal differences.
2.) is the stock plastic ignition coil connector still intact or is it missing and you only have the 2 electrical slip connectors?


Here's repost of my ignition troubleshooting test path.

How the TFI ignition works in 86-93 model Mustangs:

Tools needed: DVM, noid light, safety pin.

Theory of operation:
The TFI ignition in 86-93 Mustangs has 4 main components: the ignition switch, the coil, the TFI module and the PIP sensor inside the distributor.

The ignition switch gets power from the two yellow wires that are supplied power by a fuse link located in the wiring harness that connects to the starter solenoid.

Diagram courtesy of Tmoss & Stang&2birds


I.) The coil is mounted on the driver’s side strut tower on most EFI Mustangs. It gets power from a red/green wire and a brown/pink wire from the ignition switch. That wire from the ignition switch feeds a 20 gauge blue fuse link that connects to the red/green wire. The fuse link protects the wiring and the ignition switch, since the fuse link for the two yellow power supply wires has a much higher current rating. Without the smaller fuse link protecting the smaller wiring used in the ignition circuit, a short there would cause the red/green wire to overheat and burn up.

II.) The TFI module is mounted on the side of the distributor and supplies the ground for the coil. Every automotive power supply circuit uses the ground as the return path to carry power back to the negative side of the battery. The TFI switches the tan/yellow wire coming from the coil to ground. It gets power from the red/green wire when the ignition switch is in the Run position. The red/lt blue wire supplies a signal to turn on more power (dwell time) when the engine is cranking. The increased dwell can cause excessive current draw if the red/blue wire remains energized when the ignition switch is in the Run position. The trigger signal comes from the PIP sensor when cranking and the computer when the engine is running. The SPOUT jumper plug enables computer controlled spark advance. When the SPOUT is removed, spark advance is locked at the setting determined by the mechanical position of the distributor.

III.) The PIP sensor is in the bottom of the distributor under the shutter wheel. It is a Hall effect magnetic sensor that senses a change in the magnetic field when one of the slots in the shutter wheel uncovers the sensor. Then it supplies a pulse that triggers the TFI module to provide a ground to the ignition coil. A bad PIP will often set code 14 in the computer and cause hot start problems. Replacing the PIP sensor requires removal of the distributor and pressing the gear off the distributor shaft to expose the sensor. For most people, a remanufactured distributor ($55-$75) is the solution, since they may not have access to a press.

IV.) Troubleshooting the ignition system – no spark or weak spark. All the tests are done with the ignition switch in the Run position unless specified otherwise. A safety pin may be used to probe the wiring connectors from the back side.
1.) Check for 12 volts at the yellow wires on the ignition switch. No 12 volts and the fuse link near the starter solenoid has open circuited.
2.) Check for 12 volts on the red/green and brown/pink wires coming out of the ignition switch. No 12 volts, replace the ignition switch.
3.) Check for 12 volts at the ignition coil. No 12 volts and the blue 20 gauge fuse link has open circuited.
4.) Check for 12 volts at the red/green wire on the TFI module. No 12 volts and you have wiring problems.
5.) Remove the small red/blue wire from the starter solenoid (looks like it is stuck on a screw). This is a safety measure to keep the engine from turning while you are making measurements. Have a helper turn the ignition switch to Start and look for 12 volts on the red/lt blue wire on the TFI module. No 12 volts and you will have starting problems, but push starting the car will work OK. No 12 volts, replace the ignition switch. Be sure to reconnect the red/blue wire to the starter when you finish.
6.) Check the red/blue wire to make sure that it has less than 8 volts when the ignition switch is in the Run position.
7.) A noid light available from any auto parts store, is one way to test the PIP pulse. The computer uses the PIP signal to trigger the fuel injectors. The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and it will flash if the PIP is working. No flash from the noid light and the PIP is suspect. To confirm the PIP is being the source of the non flashing noid light, look for 12 volts on the red injector wiring. Good 12 volts and no flashing noid light means the PIP has failed.
8.) Remove the SPOUT plug from the harness and try to start the engine. If it starts, replace the PIP. This is a common no start condition when the engine is hot.
9.) The TFI module is a go/no go item when you have a no spark/weak spark condition on a cold engine. It either works or it doesn’t.
The TFI failure mode on a running car is usually a high speed miss on a warm engine. Many auto parts stores will test your TFI module for free. Bring along a hair dryer to get it hot while testing it and run several test cycles, since it often gets weak when it heats up.

The coil is somewhat more difficult to pinpoint as a problem. A good coil will make a nice fat blue spark 3/8”-1/2” long. The problem is that one person’s perception of a fat blue spark looks like may not be accurate enough to spot a weak coil. The coil is cheap enough ($13-$16) that having a known good working spare might be a good idea.

diagram courtesy of Tmoss & Stang&2Birds


TFI_5.0_comparison.gif


TFIModuletroubleshooting.jpg


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.

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

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.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 & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#7
It does not have the big block letters like the old one.
Oh okay. Does it have any Ford/Motorcraft markings at all, or does it look pretty generic like this one: http://www.walmart.com/ip/48680875?...3613489&wl4=&wl5=pla&wl6=159855744529&veh=sem

I'm trying to get a sense for whether the branded modules are less prone to arriving DOA than the unbranded ones. I know that, in theory, the branded (~$150) and unbranded (~$50) Motorcraft units should be exactly the same, and that we're essentially paying a premium for the name being embossed on the part, but I'd still like to have a spare and will pay the premium if that means that I'll get a working part.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#8
I have had nothing but problems with tfi modules from local auto parts stores. I haven't tried to find a genuine Motorcraft one yet. I should. The only one that has been working decent is the one that came on my aftermarket tfi distributor.
From what I have read, it's not entirely surprising to get a defective brand new TFI module from a local parts store, but it's troubling to be 0 for 3 on non-defective parts from fairly reputable vendors--two of which were verified to be Motorcraft.. I'd think that their quality control would be much better.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#9
1.)Was the TFI you received a gray or black one? The gray and black are indicators of some internal differences.
[/QUOTE]
Hi, Jrichker. The ones that I got were all gray, and they were all for the 5.0 manual tranny. I made sure to order the right ones.
2.) is the stock plastic ignition coil connector still intact or is it missing and you only have the 2 electrical slip connectors?
My coil connector looks like this: http://www.americanmuscle.com/ignition-coil-connector-8893.html
Not sure if it's the stock type but mine looks too new and shiny to be the factory original.

Edit: Why are there two green wires coming off of this connector? Both of my green wires are spliced into the the same single wire..
 

jAEded

Active Member
Aug 12, 2013
418
26
39
Cali
#12
This is one of the original ones. I have 2 of these.

20100719-IMG_9776.jpg





I am seeing pics of gray one on google with a Motorcraft box, but not carrying the same part number and no Motorcraft on the TFI itself.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#13
I am seeing pics of gray one on google with a Motorcraft box, but not carrying the same part number and no Motorcraft on the TFI itself.
Yuup. That's something I pointed out to Motorcraft rep, but she claimed it's still legit.

RockAuto also had an alternate part# on their site for i guess if they run out they can sub-in the same part but with a different #, but even that part# didnt match the module i got nor the box.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#14
And its funny how the units that say Motorcraft run like $150--three times cost of the unbranded ones. Makes me think that they cant be of the same quality although they are claimed to be.
 

74stang2togo

I've never done anything CT worthy...
Mod Dude
Mar 7, 2002
6,069
2,006
224
#16
Unless something has changed in the six years since I worked for Autozone, Wells manufactures both the Autozone Duralast TFI modules and the Motorcraft modules. Back then, we used to get "Duralast" modules that had the actual Ford part number stamped on them in ink and the "Motorcraft" badly ground off of the module in the Duralast boxes. Sometimes they'd even slip up and have the "Motorcraft" brand thermal paste in the box instead of the "no-name" tube.
 
Mar 7, 2016
148
9
28
Woodbridge, VA
#18
Sometimes they'd even slip up and have the "Motorcraft" brand thermal paste in the box instead of the "no-name" tube.
That's another thing! Neither of the unbranded Motorcraft unit came with the paste. The non-Motorcraft one from LMR did although it was dielectric--not thermal.
 

stpete

Active Member
Dec 26, 2015
324
158
53
52
#19
The PDI ones come with their own paste. It's unlabeled so no clue what it actually is. For all the good it does.

First module ran far enough to leave me stranded:

IMG_20160330_181552027_zpszhsnas7r.jpg


Second module only run for about 15 seconds and realized it was performing about the same as the first:

IMG_20160514_152533170_HDR_zpsx23dutnr.jpg


The white goop is the remnants of the goop they provided that I cleaned off. The black goop is the guts puking out of the module.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
26,665
2,406
224
73
Dublin GA
#20
Why are there two green wires coming off of this connector? Both of my green wires are spliced into the the same single wire..
The repair harness fits multiple Ford vehicles; some have more that 1 connection to the green wire....
 

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