Fuel problems

[stevesLX]

I have noticed that when I am idleing the car runs rich but when I drive it it runs lean. This is a 89 LX 302 w/303Fcam, 75mm TB, 24# injectors C&L MAF,Edelbrock 5.0 performer manifold and intake. I have my fuel pressure at 35 and I have tried it at 40 also and no difference. Its really weird if I idle the car for a while and then pull the plugs there are 1 or 2 that are a chocolate tan or brown but the rest of them are white to a light gray color. Now if I drive it and then pull the plugs they are all white to light gray. Some look like they are still new. They have 400 miles on them. They are motorcraft plugs gapped at .045. Any ideas at what the problem could be. Unfortunately I can not pull codes out of this car with the engine running. My check engine light wiring is no longer there. I have tried it with a voltmeter and as soon as I start the car it idles for a couple of seconds and then the meter sweeps all the way over to the right and the motor revs up real quick and then nothing. I have tried with the clutch in and out and no results. I can pull codes with engine off key on but thats it. So that is not a option on pinpointing my fuel problems.

 

[stevesLX]

nobody knows

 

[jrichker]

Fix the can't pull codes with the engine running by grounding pin 30 on the computer. Be sure that
you disconnect the ground from pin 30 before driving the car. The computer does several tests that
put the throttle under computer control and could make driving the car hazardous.

Post the codes you did get since they are the stored memory codes.


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/ Everyone should bookmark this site.

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

 

[stevesLX]

I had already posted those a few days ago they were egr and ac stuff clutch switch. Stuff that is no longer in the vehicle. So I assume that I can just use a wire and somehow hook it to pin 30 and ground the end of it to metal on the car. And then start the car and let it do its thing.

 

[jrichker]

I had already posted those a few days ago they were egr
and ac stuff clutch switch. Stuff that is no longer in the vehicle. So I assume that I can
just use a wire and somehow hook it to pin 30 and ground the end of it to metal on the car.
And then start the car and let it do its thing.

You are correct. Notice the wire color on pin 30: that will help you find the wire or trace
the problem to one of the switches or connectors that isn't working correctly.

 

[stevesLX]

pulled codes with engine running

O.K. I just pulled the codes with the engine running. I got 2 codes they are 94 and 44. Not quite sure how they would relate to my fuel issues with idleing rich and running lean. I really dont think they are connected at all. I only have 2 plugs that seem to get chocolate brown the rest of them are a grayish color or they are white. When you are idleing you can smell how rich its burning.

 

[jrichker]

What about the cylinder balance test? It will help isolate any injectors that may not be working properly.

 

[stevesLX]

cylinder balance test

I just did the cylinder balance test 3 times and all 3 times I got 9 sweeps on the voltmeter. You know when I did the code test the first time tonight I got a code 21the first time. It repeated itself 2 times just like the others did. But I performed the code test 2 more times after that and code 21 never came back up again. And when I did the cylinder balance test just before waiting for it to go thru the code deal again so I could perform the balance test code 21 didn't come up that time either. Just the very first time tonight thats it.

 

[stevesLX]

O.K.

 

[jrichker]

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 :

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

Note that all resistance tests must be done with power off. Measuring resistance
with a circuit powered on will give false readings and possibly damage the meter.

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

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