mass air problems

[fastford91]

ok i know i posted my problem last time! my car still has code 66 which is no voltage or low voltage to mass air! i have that part! ok so here's what i have done so far ! winter is over and it's time to pull out the old stang again! and i want it running right with the mass air pluged in this time! LOL! anyway today i checked the voltage on the red wire and the black wires and i have 12 volts there! then i took off the electrical part off ! that being the lil black thingy on top! now i tested it there on the elements for 12 volts! my question is should it be 12 volts at the elements to or will it be a lower reading ? cause when i tested it like that i didnt get 12 volts at the element! so if im susposed to get 12 volts at the element and im not im guessing the electrical part is pooched! any thoughts on this? and dont tell me to check the wires again for 12 volts i already have! also all the wires on this thing are mint cause its never been driven in the winter since new!!:SNSign:

 

[jrichker]

Read all of the code 66 description. The answer to your questions are in there.

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.

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).

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. 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 ground. 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

 

[fastford91]

ok read that been there done it! i just need to know if there should be 12 volts on the elements or not! a simple yes or no would be more helpful!

 

[jrichker]

ok read that been there done it! i just need to know if there should be 12 volts on the elements or not! a simple yes or no would be more helpful!

The A & B wires are for the heater element. They will have 12 volts across them any time the ignition switch is in the Run position.

The C & D wires are the signal output. They will have a voltage output across them that varies with engine speed.

See my post for the voltage values on the C & D wires with the engine running.

 

[fastford91]

ok thank you ! it was there infront of me the whole time! i guess i read into things to much and get confused! thank you! but what if i chaeck all that and everything checks out ok and i still get the 66 code? and ideas what to look for next ? o2 sensors? any other ideas? but will check what you have told me first! thank you !