Changed the TFI, Mustang still shutting off after about 10 minutes

Discussion in 'Fox 5.0 Mustang Tech' started by jim5point0, Mar 17, 2013.


  1. jim5point0

    jim5point0 New Member

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    All, Two weeks ago the Mustang began to shutdown on the highway. A few years ago this happened and I changed the TFI and everything was fine. I figured the TFI must have went bad again. I changed the TFI. Went down the road and the car shutoff. Towed the car home. Figured the TFI couldn't be bad becuase it was new. I then changed the PIP sensor to rule that out and I also changed the coil as they were original. Car started and shut off after about 10 minutes. Traced from the coil to the distributor with the test light. Pointed to a bad TFI. Put in an old bad Ford TFI that I had and the car started right up. Figured I must have purchased a bad TFI. Went back returned the TFI and then bought a Ford TFI. Figured the after market was not good. Put the new TFI in yesterday, took a short test drive about 10minutes, came home as I was parking the car shut off and wouldn't start. Immediately put an old Ford TFI in and the car started right back up.

    My Mustang is a stock 1987 5.0 Automatic an is my daily driver. 123k miles.

    Any Idea? The car is in great shape. Seems like the TFI is getting too hot too fast. I can't imagine I have purchsed two bad TFIs. Once it is cool i will start.
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  2. jim5point0

    jim5point0 New Member

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    Also, I did use the greese between the TFI and distributor.
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  3. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    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.

    To remove the gear, first you drive out the roll pin that secures the gear to the shaft. Then you get to press the gear off with a hydraulic press or puller. When you go to press the gear back on, it has to be perfectly lined up with the hole in the gear and shaft. I have been told that the hole for the pin is offset slightly from center and may require some extra examination to get it lined up correctly.

    Most guys just end up replacing the distributor with a remanufactured 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.

    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.
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  4. jim5point0

    jim5point0 New Member

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    jrichker, Very good information and links. Thanks. Today I bought a new distributor ready to go in and includes the pip and tfi. Although I changed the PIP (pulled and pressed gear, etc.). We''ll see. I'l let you know.
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  5. jim5point0

    jim5point0 New Member

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    ok, tonight I set TDC then put the new motorcraft distributor in that I bought at NAPA. The distributer included a TFI already installed and of course the PIP sensor installed as well already installed. Pulled the SPOUT. Set the timing and started the car. Reached operating tempature and then I let it run for about 15 minutes. The car didn't shutoff after 10 minutes. So maybe the problem is solved. Tomorrow night I'll drive it around the neighborhood for another test. I can not explain it, unless I had previosuly purchased two bad TFIs or a bad PIP sensor and messed up the install. I'll report back tomorrow.
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  6. jim5point0

    jim5point0 New Member

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    Got home started the Mustang. Went in and ate dinner. After dinner, the Mustang was still running and warmed.Took the car for a ride and put about 18 miles on it. The problem seems to be resolved. I'll keep you posted.
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