Engine Erratic running… spittin’ and sputtern’

Discussion in 'Fox 5.0 Mustang Tech' started by Mr67Stang, Apr 3, 2013.


  1. Mr67Stang

    Mr67Stang Active Member

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    I recently swapped the AOD out of my ’91 GT for a T-5. The car ran fine before and for 200+ miles after that swap. Suddenly, yesterday, I took the car to work and no more than one minute after leaving the house I notice it miss firing a little. Progressively and rather rapidly it got worse. By the time I got off work and was heading home with it was so bad that the misfiring was causing the car to lurch and buck like a Bronco rather than a Mustang. The car was due for a tune up anyway so, I immediately replaced plugs, wires, cap, rotor and even got a new coil. I did NOT replace the electronic control module on the side of the distributor. I did recently change the solinoid (200+ miles on it) but even more recently, I just filled the gas tank up probably 25 miles before it started acting up.
    Therefore, I am beginning to believe it may be a fuel problem since every plug I removed was dry and brownish red in color. What is the best way to trouble shoot the fuel system? I do have a fuel pressure tester somewhere in the black hole of tools I call my shop. If I have good pressure at the fuel rail, is it pretty safe to assume the problem is in the injectors? Poor pressure at the fuel rail could be anything from the regulator back to the tank. I believe my injectors are 22 year old originals.
    Other possible causes? TPS, IAC, Computer, bad muffler bearings :bang:
    #1
  2. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    I once went to a gas station and the 93 octane underground tank was filled mistakenly with diesel. Needless to say that was an adventure and really tore some stuff up, lol.

    Check the fuel pressure first and if it has been a while then change the fuel filter while your at it. It is possible to that you simply got bad gas. With the fuel filter out pump some fuel into a clear jug and see if there is water or anything crazy in it. Good luck and keep us posted..
    #2
  3. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    Muffler bearings, lmao ^^^^^
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  4. elarm1

    elarm1 Active Member

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    I would first test the modules in the Distributor. Sounds like CPS problems to me
    #4
  5. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    Any codes?
    #5
  6. Mr67Stang

    Mr67Stang Active Member

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    Yea, I already ruled out dirty brake light fluid:)

    I do not have a check engine light on but I know it can throw a code without the light comming on.

    This is what it feels like!

    I will likely not have time to do much until the weekend so I was hoping for some good ideas as to where/how to look. The pump some fuel into a jug is a good one that may be the first thing I do after the pressure test. I hate having to get under the car. I'm 42 and it keeps getting harder to get back up afterwards.
    #6
  7. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    run the codes? Many do not trigger the cel but will tell you whats going on
    #7
  8. Mr67Stang

    Mr67Stang Active Member

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    Took a little time after work today and put the fuel pressure test to it. I got 10 lbs turning the key on, 34 lbs after starting and 42 lbs after removing the vacuum from the regulator. Sounds normal to me. I purged some fuel 1.5 quarts'ish from the bypass on my pressure tester and put it in a clean glass jar. It looked like pickle juice. I put my nose deep into the jar and inhaled deep and it barely phased me. I work with gas a lot and this stuff smells WEAK. I could probably get more fire from my **** after a good night of drinking.

    So, what's the easiest way to drain a Fox tank? My ole '67 has a drain plug;)
    #8
  9. Mr67Stang

    Mr67Stang Active Member

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    Here is what the gas looked like.

    Attached Files:

    • Gas.jpg
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    #9
  10. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    ^^ That doesn't look right. Are you sure it's not pickle juice? lol Did you wind up draining the whole tank? How did you make out otherwise?
    #10
  11. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    that aint what my gas looks like :eek:
    #11
  12. mikestang63

    mikestang63 Mustang Master

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    Hell.......i'd drink that there right down Jack!

    [​IMG]
    #12
  13. HuskerNation

    HuskerNation Member

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    That gas doesn't look good at all! I would be tempted to call the station you filled up at, and as them if they have had any recent problems reported. They may inform you of a mix up or some other reports. There are syphoning (sp?) kits out there. Drain it enough where you can drop the tank out and give it a good cleaning too.
    #13
  14. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Pumping out the old gas:
    If the old pump still works, you can use it to pump the tank out. You will have to watch the output so that when the flow volume starts to drop that you shut it off. Running the fuel pump dry isn't a good thing.
    1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
    Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.
    [​IMG]

    Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

    2.) Jumper the fuel pump test point to ground.

    [​IMG]

    Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.
    #14
  15. Mr67Stang

    Mr67Stang Active Member

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    Thanks for that! I did not want to have to sit in the car and turn the key back and forth for 4 hours.

    I am concerned now there may be other issues as the car is running even worse now. Can anyone tell me what the symptoms are of bad O-2 sensors and or bad Mass Airflow sensor? Still, no light on the dash but I think I will go ahead and see if it has any stored codes.
    #15
  16. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

    Dumping the computer diagnostic codes on 86-95 Mustangs

    Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

    Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

    Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

    Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

    Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
    Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

    [​IMG]

    [​IMG]

    If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

    [​IMG]

    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

    [​IMG]

    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


    WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

    What to expect:
    You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

    Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

    Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

    Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

    Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
    See AutoZone Part Number: 25886 , $10
    [​IMG]



    Alternate methods:
    For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

    Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30-$36.
    #16
  17. pearlnotchback

    pearlnotchback Active Member

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    looks like pee
    #17
  18. Mr67Stang

    Mr67Stang Active Member

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    Okay, I pulled the codes... Of note, I think the most vital and probably the problem is 14 - PIP circuit failure I also got 33,66, and 96. I am not well versed in 5.0 Fox tech but I have read that the PIP has something to do with the distributor. I have no idea what a PIP is but if it has to do with the ignition then I would start with this based on my symptoms. What say the 5.0 Fox experts?
    #18
  19. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Code 14 - Ignition pickup (PIP) was erratic – the hall effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts.

    Revised 10-Dec-2012 to add PIP diagnostic testing & Wells info

    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:
    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.

    Code 33 - Insufficient EGR flow detected.
    Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal changes. Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
    Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

    Backside view of the computer wiring connector:
    [​IMG]

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

    http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

    http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


    EGR test procedure courtesy of cjones

    to check the EGR valve:
    bring the engine to normal temp.

    connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

    Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).


    apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

    if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

    if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

    if engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
    Use your finger to cap the open port on the vacuum tee.
    snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
    did the vacuum gauge show about 2-5 in vacuum?
    if not the EVR has failed

    EGR test jig
    [​IMG]

    The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.

    Code 66 MAF below minimum test voltage.
    Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

    There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables. Changes in RPM causes the airflow to increase or decrease, changing the voltage output.. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

    The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).


    Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

    At idle = approximately .6 volt
    20 MPH = approximately 1.10 volt
    40 MPH = approximately 1.70 volt
    60 MPH = approximately 2.10 volt

    Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

    There should be a minimum of 10K ohms between either pin C or D on the MAF wiring connector and pins A or B. Make your measurement with the MAF disconnected from the wiring harness.


    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/

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

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

    Computer,. actuator & sensor wiring
    http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

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

    Vacuum routing
    http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

    Code 96 causes & tests 91-93 models. – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump circuit lost power at one time or another.

    Revised 07-apr-2013 to add check for corrosion and damage in fuel pump relay socket

    Clear the codes by disconnecting the battery and turning on the headlights for about 5 minutes before reconnecting the battery. This will clear any remaining codes. Drive the car for several days and dump the codes again. In many cases, this clears the 96 code.

    Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier model cars is under the passenger seat. On Mass Air Conversions, the signal lead that tells the computer that the fuel pump has power may not have been wired correctly. See Mustang Mass Air Conversion | StangNet

    Diagram of the fuel pump wiring for 91-93 cars.
    [​IMG]

    Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. No voltage when jumpered, check the fuel pump relay and fuse links.

    [​IMG]


    Power feed: Look for 12 volts at the pink/black wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, or connections. Remember that on 92 or later models the fuel pump relay is located under the Mass Air meter. Watch out for the WOT A/C control relay on these cars, as it is located in the same place and can easily be mistaken for the fuel pump relay.

    Relay: Turn on the key and jumper the ECC test connector as previously described. Look for 12 volts at the dark green\yellow wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit. Be sure to closely check the condition of the relay, wiring & socket for corrosion and damage.

    [​IMG]

    91-93 Models:
    Using the diagram, check the dark green/yellow wire from the fuel pump relay: you should see 12 volts or so. If not the relay has failed or is intermittent. Check the inertia switch: on a hatch it is on the drivers side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Pink/black wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the dark green/yellow wire, swap the relay.

    All testing is done with the ignition switch in the Run position. Do not forget this crucial step.

    The pink/black wire s should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the fuel pump has opened up.

    With the test jumper in place the green/yellow wire should be the same voltage as the pink/black wire +/- 0.25 volt.

    If not, look at the red wire: should have the same voltage as the battery positive terminal +/- 0.25 volt.
    If not, then check the yellow wire on the EEC relay located on top of the computer. This one is hard to get to. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the computer has opened up.

    If the red wire does not have the same voltage as the battery positive terminal +/- 0.25 volt and the yellow wire on the EEC relay does, then check the red/green wire on the EEC relay. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the ignition switch is defective or the fuse link in the ignition wiring harness has opened up, or the EEC relay is defective.

    All testing is done with the ignition switch in the Run position. Do not forget this crucial step.

    The pink/black wire s should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the fuel pump has opened up.

    With the test jumper in place the green/yellow wire should be the same voltage as the pink/black wire +/- 0.25 volt.

    If not, look at the red wire: should have the same voltage as the battery positive terminal +/- 0.25 volt.
    If not, then check the yellow wire on the EEC relay located on top of the computer. This one is hard to get to. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the computer has opened up.

    If the red wire does not have the same voltage as the battery positive terminal +/- 0.25 volt and the yellow wire on the EEC relay does, then check the red/green wire on the EEC relay. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the ignition switch is defective or the fuse link in the ignition wiring harness has opened up, or the EEC relay is defective.

    Diagram courtesy of Tmoss & Stang&2birds
    [​IMG]


    O2 Sensor harness interchange and modification

    Originally Posted by 302EFI


    Revised 16-Oct-2011 to add O2 sensor harness warnings
    The wires for the 02's and low oil did not change throughout the years, they are all in the same place.
    The main ones you need to worry about are (on the harness end (ECU) that plugs into the 02 plug) is:
    \- 1. Lightblue / yellow
    - 2. White / Purple
    - 3. Purple / Yellow
    The White/Purple & Purple/Yellow gets looped for a automatic ECU
    The Purple/Yellow & Lightblue/Yellow for a manual ECU

    See http://forums.corral.net/forums/gen...manual-auto-differences-year-differences.html for more O2 sensor wiring harness info

    Basic premise to use with transmission swaps:
    Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
    Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
    See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

    90 model year harness only works with 90 model cars without inspection/rework.
    The 4 cylinder O2 harness uses 4 wire O2 sensors. It probably won’t work correctly without modifying it.
    #19
  20. Mr67Stang

    Mr67Stang Active Member

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    I already removed my distributor and removed the "cup" looking thing and saw that the magnet has been making contact with the inside of it and the magnet on the PIP is loose. Probably just going to go get a reman distributor. I think it's toast and my urinr colored fuel is probably fine since I pumped out 5 gallons and put it in my 2.3L Fox and had no problems.
    #20

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