car starts but dies right away

fuel pump relay kicking over to run pos.

Carbs rule man............ Peace

Code 21 is Engine coolant temp sensor out of range
Code 23 is TPS out of range or set to high
Code 24 is Intake air temp sensor out of range

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

The tps is most likely bad That would cause your car not run unlless you feathered the pedal.

Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor.
Note that that if the outside air temp is below 50 degrees F that the test for the
ECT can be in error.

The ECT sensor has absolutely nothing to do with the temperature gauge. They are
different animals. The ECT sensor is normally located it the RH front of the engine in
the water feed tubes for the heater.

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate
readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is
a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower
intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from
the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
so that you don't damage the wiring or connector.

Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

Diagram courtesy of Tmoss & Stang&2birds



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, 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



Code 23 - Throttle sensor out of range or throttle set too high - TPS needs to be reset to below 1.2 volts at idle. Keep in mind that when you turn the idle screw to set the idle speed, you change the TPS setting.
You'll need a Digital Voltmeter (DVM) to do the job.

Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

Always use the Dark Green/lt green & Black/white wires to set the TPS base voltage.

Do the test with the ignition switch in the Run position without the engine running.

Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.

When you installed the sensor make sure you place it on the peg right and then tighten it down
properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw
enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using
marks. Set it at .6.v-.9 v.

1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you
can and get it nice and warm.

2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into
the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the
TPS and the other to ground.

If setting the TPS doesn’t fix the problem, then you may have wiring problems.
With the power off, measure the resistance between the black/white wire and battery ground.
You should see less than 2 ohms. Check the same black /white wire on the TPS and MAP/Baro
sensor. More than 1 ohm there and the wire is probably broken in the harness between the engine
and the computer. The 10 pin connectors pass the black/white wire back to the computer, and can
cause problems.

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

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

See http://fordfuelinjection.com/index.php?p=6 for more wiring help & 10 pin connector diagrams

Code 24 - Intake Air Temperature (ACT) sensor out of range. Bad sensor, bad wiring.
The ACT for Mustangs built before 95 is in the #5 intake runner. It measures the air temperature in
the intake to help computer the proper air/fuel ratio.

Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

ACT & ECT test data:

The ACT & ECT have the same thermistor, so the table values are the same

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if
the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage
readings will be lower because of the heat transfer.
Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

Jrichker said it better than me. I knew the ECT had nothing to to with the temp guage. I should of explain it better.Thats why you are stangnets favorite tool.

Some punctuation will make your post easier to read. I normally don't respond to posts that don't use punctuation.
It seems that my technical descriptions are too advanced for people that can't use proper punctuation and grammar.

Go back and re-read the code 23 test path – you’ll find this step which you may have skipped.
“If setting the TPS doesn’t fix the problem, then you may have wiring problems.
With the power off, measure the resistance between the black/white wire and battery ground. You should see less than 2 ohms.
Check the same black /white wire on the TPS and MAP/Baro sensor. More than 1 ohm there, then the wire is probably broken
in the harness between the engine and the computer. The 10 pin connectors pass the black/white wire back to the computer,
and can cause problems.”

Check the fuel pressure when the car starts and dies. There is a Schrader valve on the pressure line near the quick disconnect
coupler for the engine fuel rails. Most auto parts stores will rent or loan a fuel pressure test gauge. Disconnect the vacuum line
from the fuel pressure regulator and plug the line that goes to the manifold so you don't create a vacuum leak.
You should see 38-40 PSI when starting and it should hold that pressure for at least 10 seconds after the engine shuts off.