Lx Left Me Stranded Again

LarsD · Aug 16, 2014

modulistic said:
I had a bad pip that took out my tfi module. Mine also died suddenly, replaced tfi, then ran great until it got hot and would start ****ing up again.

stykthyn said:
If it's your pick up try pulling out the spark advance plug next time it dies. I had this happen on a reman distributor abd it would die with the plug in.

Is there anyway to test this? I hope my new TFI isn't ruined. This is ridiculous, I am about ready to throw all this EFI stuff in the garbage and put a carb on the car. I drive through to many construction areas with high traffic to just "drive it till it dies again" it is too dangerous.

When the car was dead I poured some water on the TFI and it's heatsink to see if it would crank and the car didn't change it's attitude at all.

stykthyn · Aug 16, 2014

Do you have on old distributor? If not grab one from the jy.

2000xp8 · Aug 16, 2014

stykthyn said:
Do you have on old distributor? If not grab one from the jy.

Yup, this is the easiest and probably cheapest solution.

LarsD · Aug 18, 2014

Junk yards around here don't have 5.0's anymore. I figure it is one of three things at this point. Either it is the PIP sensor, the coil (it is the original 150K mile unit as far as I know), or something in my EEC. I have a Quarter Horse installed, and when I tried to pull codes on the car yesterday I got nothing out of it, not even the 11 system OK code. Now it might be disabled by the Quarter Horse, I am not sure, I have not tried to pull codes on the car since I installed it. I could remove it from the car, but I have 30lb injectors and a 24lb MAF on the car. The QH is adjusted for it, but I never have trusted it since the software is the most buggiest pos I have ever used. I would have to buy a properly cal'd meter so that the car could run properly without the QH. I pulled a couple of plugs at random and they are slightly white, so the car is running a bit lean as well, though I have never heard any knock from the car (no specs on the plugs either).

jesse325 · Aug 18, 2014

my 88 is doing the same thing, as of now the only thing ive came up with is im loseing fire, cant pull the stalling trouble shooting check list up. but the tfi has been tested and the dizzy has maybe 15 miles on it

jrichker · Aug 18, 2014

Computer will not go into diagnostic mode on 91-93 model 5.0 Mustangs

How it is supposed to work:
The grey/red wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector grey/red wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60. Only an experienced electronics technician can open the computer up & repair the trace if it burns up and creates an open circuit.

The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (grey/red wire) on the self test connector and battery ground. You should see less than 1.5 ohms.

If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the grey/red wire and pin 46 on the computer wiring connector : it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More that that and the computer’s internal ground has failed, and the computer needs to be replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.

Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the grey/red wire goes. Almost every sensor on the engine except the MAF is connected to it.

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

See the graphic for the 10 pin connector circuit layout.

jesse325 · Aug 18, 2014

Mine dose not have a grey red at the Sti, it has what looks to be a red green, white black, yellow black, would I use the red green? I don't wanna burn up anything

jrichker · Aug 18, 2014

The wiring and some wire colors changed starting in 1991. The 1987-1990 model cars all has the same wires colors.

If you need help for a similar problem, please start your own separate post.

jesse325 · Aug 18, 2014

Sorry just seen for the different years was looking at the wrong thing like a Chevy guy would ok I'm going to lol in the right spot

LarsD · Aug 23, 2014

Well I rechecked it, turns out I jumper'd to the wrong wire, so the car was running in self diagnostic mode, so not a problem there. Although I did check the grounds. From the STI connector to the computer ground measures 4K, and from the computer ground to battery/chassis ground measures 7 ohms. Neither of which seems to be correct.

jrichker · Aug 23, 2014

LarsD said:
Well I rechecked it, turns out I jumper'd to the wrong wire, so the car was running in self diagnostic mode, so not a problem there. Although I did check the grounds. From the STI connector to the computer ground measures 4K, and from the computer ground to battery/chassis ground measures 7 ohms. Neither of which seems to be correct.

Disconnect he battery and see if that changes anything.

LarsD · Aug 30, 2014

OK, I replaced the coil and the MAF with a 30lbs calibrated MAF. That way I could remove the QH to eliminate it from the suspect list. Since I had the ECU out I checked from the grey/red wire and pin 46. I got 1.8 ohms. I imagine that is close enough. Going to check the other connections and the ECU next.

ETA: OK, ECU checks out fine at 1.3ohms, STI wiring is right on the nose at 1.4 to 1.5 ohms. Guess the car's wiring is good.

LarsD · Aug 30, 2014

OK, I will have to try and pull codes to see if anything pops. I test drove the car, it runs better then ever with the new meter and the Quarter Horse removed. I will chalk this up to incompatibility between me and the QH (as I never had a problem with TwEECer).

LarsD · Sep 21, 2014

Tried to pull codes. Nada, got code 11 and that's it. Ordered a PIP module, not sure if it will be worth the trouble to swap out or not.

jrichker · Sep 21, 2014

PIP Sensor functionality, testing and replacement:
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, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, 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.

LarsD · Sep 21, 2014

jrichker said:
PIP Sensor functionality, testing and replacement:
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, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, 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.

Thanks jrichker, gives me some stuff to run down before I got through the trouble.

LarsD · Feb 14, 2015

Been a long time but I finally have an update. I did the measurements that Jrichker suggested and everything looked OK. I replaced the unknown mfg pip sensor that Performance Distributor used with a new Ford PIP module. Fired the car up, set the timing, and I let it warm up. Everything seemed fine up until right before I pulled it out of the garage. I noticed it felt like the car was starting to load up at idle so I went to rev it up a little and it started to pop out of the exhaust. It has never done this before, other then that last time it left me stranded and it was struggling to stay alive. I could let it idle, it would idle rough, then I would try to rev it slowly to 2K rpm. When it hit approximately 1600 rpm it would start stumbling and popping out of the exhaust. I would push it further and it would do it at 2K rpm also. I shut it down and looked over the plug wires, nothing was grounded out. I noticed the MAF plug looked like it had backed out so I reseated it. Once I re-fired the car it seemed to run better other then idling high (1200ish rpm). I adjusted the idle speed screw on the TB (engine off), until the idle was back down to about 900 rpm. Car seemed fine, then started loading up and popping again when I would attempt to rev it to 2K.

I gave up and shut it off. While walking back to the house I thought I would try unplugging the SPOUT connector and see what it did. Low and behold the car ran clean. I let it idle for a bit, would rev it, and no popping. As soon as I plugged the SPOUT back in the popping resumed. At this point I am under the assumption that there is something wrong in the PCM and/or it's wiring.

jrichker · Feb 15, 2015

Dump the codes again and see what you get. If all you get is an 11, and your pip wiring resistance checked out good, the computer is all that is left. Disconnect the battery and remove the Quarterhorse hardware. There is a possibility that it did some goofy stuff in the computer program that will go away when the computer power and keep alive voltage is disconnected..

LarsD · Feb 15, 2015

jrichker said:
Dump the codes again and see what you get. If all you get is an 11, and your pip wiring resistance checked out good, the computer is all that is left. Disconnect the battery and remove the Quarterhorse hardware. There is a possibility that it did some goofy stuff in the computer program that will go away when the computer power and keep alive voltage is disconnected..

I replaced the 24lbs MAF with a 30lbs MAF so I could remove the QH. It is no longer on the car. I'll check the codes/wiring again.

LarsD · Feb 16, 2015

Weill I figure out the popping problem. Turns out I installed the new sensor incorrectly. There is a locating dowel inside the distributor that the PIP sensor keys onto, well I missed the pin. So when the computer was trying to control the timing it was getting cross talk on the reluctor wheel and messing up the firing order.

Lx Left Me Stranded Again

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I want to measure mine. It doesn't look that tall.

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