Engine 92 Vert Dies In Drive

JAZ 5.0 · Feb 18, 2014

Hello all, It's been a long time since I've been on this board and have returned because I'm having problems with my 92. It's a 92 GT vert with about 154k miles. Original motor. The only mods have been a Bbk catted h pipe. Flowmaster cat back. Msd distributor. (Good deal at the time) drop in k&n. Ford racing plug wires. I think that's all.

Now I've had the car for 13 years and kinda stopped driving it when I bought my second mustang. So since about 2006 it's been sitting more than driven. But there were periods were I drove the car consistently. It just hasn't been sitting without firing for 7 years. I would drive the 5.0 consistently from time to time during that period.

So here's the problem. Car fires up. Runs with a slight miss, little shaky idle. No big deal. Maybe bad bass. When you put it into drive, the car either dies or starts missing really bad. Very rough idle. And if you try to accelerate while in drive, it very slowly climbs rpm's, like it's bogging down, and black smoke comes out the exhaust. Back in Park, the car runs fine, with a slight miss, and revs up fine. With no smoke or rough miss.

We've been stumped on this. Don't know how to fix this. We've changed the neutral safety switch. Ignition module. Distributor. Nothing has improved. The weird thing is that sometimes you'll fire her up and throw her in drive and she'll run fine. No problems. Then after driving for a while, she'll start acting up as described. I need help fixing this please...I want to start driving my 5.0 again as good top down weather approaches. Asking around, I've been told the torque convertor or timing chain....any ideas or insight?

jrichker · Feb 18, 2014

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.

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.

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.

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

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 www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.

JAZ 5.0 · May 26, 2014

Ok, well I've dumped codes and I've gotten them all. Because it's running like sh!t all sensors are throwing a code. Clearing codes and running codes when it's just on and not dropping it in drive yields nothing.

Anyone had similar experience? Any ideas of where to start looking? Replacing? Checking?

jcgafford · May 26, 2014

JAZ 5.0 said:
Ok, well I've dumped codes and I've gotten them all. Because it's running like sh!t all sensors are throwing a code. Clearing codes and running codes when it's just on and not dropping it in drive yields nothing.

Anyone had similar experience? Any ideas of where to start looking? Replacing? Checking?

List all the codes you got before clearing them. Let the engine run for a few minutes now that you cleared the codes and re dump them. List all the new codes. Dont start replacing parts till you get some direction on all the codes.

jrichker · May 26, 2014

Disconnect the battery for 5 minutes. That will clear the codes. Drive the car for 30 minutes to get the computer to relearn the sensor output. Then dump the codes again.

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.

JAZ 5.0 · May 26, 2014

I wrote the codes down and I'll post them up. Since I've cleared them it shouldn't have any right now. I'll run it but if I just turn it on and let it run, it runs fine. It's only when I place it in drive that it dies. I have to put it and drive and essential power brake to keep it alive. Otherwise, it just dies. But I'll try to pull codes again.

And just to note, there were no hard codes. Check engine light doesn't turn on after running the car in park.

But as soon as I can I'll list the codes.

jcgafford · May 26, 2014

The codes unfortunately are real. The cel hardly ever will stay on with any combo of codes. Post em up!

JAZ 5.0 · Jun 1, 2014

Ok, I have codes. So hopefully this will narrow down the problem....

These codes are the first codes pulled a long time ago...
KOER
94 - Secondary Air Injection Inoperative. bank two, driver side (R), Torque Converter Clutch Solenoid Circuit Failure (O)
44 - Secondary Air System Inoperative. bank one, passenger side (R)
21 - Engine Coolant Temperature (ECT) Sensor Out Of Self Test Range. 0.3 to 3.7 volts(O,R)
Second time
13 - RPM Not Within Self Test Upper Limit (R), Idle Speed Control motor or Air Bypass not controlling idle properly -generally idle too high
93 - Converter Clutch Solenoid Circuit Failure (O)
44 - Secondary Air System Inoperative. bank one, passenger side (R)

First codes pulled were yesterday were
KOEO
11 - System Pass (O,CM,R)
15 - Readout Memory Test Failed (O), Keep Alive Memory Test Failed (CM)
65 - Transmission Control Switch/Overdrive Cancel Switch Circuit Did Not Change States (R)
49 - 1–2 Shift Error (CM)

Second time
56 - Mass Air Flow/Vane Air Flow Sensor Circuit Above Maximum Voltage (O,CM,R), MAF Sensor short to power (CM,R), Transmission Fluid Temperature Circuit Open (CM,O)
96 - Fuel Pump Circuit Open-Battery To PCM (CM,O)

jrichker · Jun 1, 2014

First off, the AOD doesn't communicate with the computer, only the AODE used in 94 or later Mustangs does that. That means you may have missed a flash if you used the counting flash method when you dumped the codes.

Going on that basis, here's what you probably have.

Code 15 - No Keep Alive Memory power to PCM pin 1 or bad PCM (Memory Test Failure). The voltage to the Keep Alive Memory (KAM) is missing (wiring problem) or the KAM is bad. The KAM holds all of the settings that the computer "learns" as it operates and all the stored error codes that are generated as a result of something malfunctioning while the engine is running. Use a voltmeter to check the voltage to the pin 1 on the computer - you should always have 12 volts. No constant 12 volts = bad wiring. If you do always have the 12 volts, then the KAM is bad and the computer is faulty.

If the computer has to "relearn" all the optimum settings every time it powers up, the initial 5-30 minutes of operation may exhibit surges, poor low speed performance, and rough idle.

Note that some aftermarket chips will cause code 15 to set. Remove the chip, clear the codes and retest.

Before replacing the computer, remove the battery ground cable for about 20 minutes. This will clear all the codes. Retest after several days of running. If the 15 code is gone, then don't worry about it. If it is still there, then you get to do some
troubleshooting.

See the following website for some help from Tmoss (diagram designer) & Stang&2
Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Diagram courtesy of Tmoss & Stang&2birds

ECC Diagram for 91-93 5.0 Mustangs

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

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

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Code 66 or 157 MAF below minimum test voltage.

Revised 10-Feb-2014 to add 95-95 Mustang code 157 and 94-95 ECC diagram

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.

Computer connector for 88-93 5.0 Mustangs

Diagrams courtesy of Tmoss and Stang&2Birds

ECC Diagram for 91-93 5.0 Mustangs

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).

89-90 Model cars: 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.

91-95 Model cars: Measure the MAF output at pins C & D on the MAF connector light blue/red 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.

Actually MAF pins C & D float with reference to ground. The signal output of the MAF is a differential amplifier setup. Pins C & D both carry the output signal, but one pin's output is inverted from the other. The difference in signal between C & D is what the computer's input circuit is looking for. The difference in the two outputs helps cancel out electrical noise generated by the ignition system and other components. Since the noise will be of the same polarity, wave shape and magnitude, the differential input of the computer electronically subtracts it from the signal. Then it passes the signal on to an Analog to Digital converter section inside the computer's CPU chip.

Code 56 MAF - output voltage too high. Failed MAF sensor, short between MAF sensor and heater or short in wiring between pin A (12 volts) and pins C or D.

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.

The MAF output varies with RPM which causes the airflow to increase or decease. 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. 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.

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

Disconnect the MAF sensor, battery negative post and computer connector. The computer connector is located under the passenger side kick panel & is secured by a single 10 MM bolt. Do not make any resistance checks without disconnecting the connectors. You will get incorrect readings.Check the resistance between the MAF signal wiring and power. Pin D on the MAF (dark blue/orange wire) and Pin A (red wire) should be 1 megohm or higher (meter shows infinite resistance or open circuit.). Pin C on the MAF (tan/light blue wire) and Pin A (red wire) should be 1 megohm or higher (meter shows infinite resistance or open circuit.).

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

ECC Diagram for 91-93 5.0 Mustangs

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.

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.

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.

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

It looks like you have some problem with the MAF. Disconnect it for troubleshooting purposes and see if it changes the problem symptoms.

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

JAZ 5.0 · Jun 1, 2014

Ok, so one code and the condition of the car wouldn't trigger the rest of the codes to activate? For example, I don't think my car is running in a poor condition because all these things are wrong. It's running in poor condition because some ONE thing is wrong but because of the poor condition, the computer is also sensing other sensors to be having issues. In essence, a false positive. So which would be the one to most likely be the issue to narrow it down?

jcgafford · Jun 1, 2014

JAZ 5.0 said:
Ok, so one code and the condition of the car wouldn't trigger the rest of the codes to activate? For example, I don't think my car is running in a poor condition because all these things are wrong. It's running in poor condition because some ONE thing is wrong but because of the poor condition, the computer is also sensing other sensors to be having issues. In essence, a false positive. So which would be the one to most likely be the issue to narrow it down?

I had the same train of thought with my 92. Some things may actually be triggering more than one code. In reality though it is usually quite a few things that are wrong with these 20+ year old cars. At least your list is a quarter as long as mine was. Jrichker got me thru all of them and my vert is code free. It did take some work though. Good luck.

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