problem with mass air conversion

Is The MAP sensor still connected to vacuum? If so, disconnect it and cap the vacuum line on the manifold. The MAP gets vented to the outside air.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link 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.



See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

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.

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.

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

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is less than $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

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.

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 and ground.

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

check what your base idle is set at...if it is too low then it will need to use the iac at idle, ad it will not idle with the iac unplugged. also check the tps voltage. jrichker can help with that stuff better than i.

hmm weird...so it only has increased idle with the iac plugged in? hmm...have you tried a different iac? and where do you get that 100% number from? my understanding was that although the ngs supports data stream, the eec-iv's did not have this capability. you dont have a vacuum leak if it idles without the iac. the iac will not set a code on the first ignition cycle, ie the light doesnt come on if youre just setting base idle. it is possible that you have a short to ground on the iac wiring. you know, constant power, eec-controlled ground. when you say it runs without the intake tube attached, is the mass air plugged in or not?

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=534062
for help with your idle problems. The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

With the IAC unplugged put your hand over the throttle body and see if it still runs. If so, it is a vacuum leak. I suspect you've got a wiring issue, as in you've got the MAF hooked up wrong. Check the wires with it unplugged with the Ford EVTM and see if everything has what it should. I think maybe you've got the power wire switched. Whoever said you don't have a vacuum leak if the IAC is unplugged and it still idles is evidently high. The IAC is a metered vacuum leak, after all. If you've got the IAC unhooked and adjusting the idle doesn't change anything then something is amiss. Do you have the MAP sensor vacuum port open to the atmosphere? It should be. I'm also a ford tech and you're embarrassing me here.

blue87stang said:

Thats the thing i cant get the base idle to set , even with the iac unplugged it seems to let air through. Like i said before i am a ford tech and this is what i do for a living but i never seen this problem before. tp is set to spec with out the iac plugged in it idles at like 600 rpms, and wont really change from that, with the iac plugged in it wont even idle it just opens up all the way.

Click to expand...

if you can get it to idle at 600 rpm with the iac unplugged then YOU HAVE THE BASE IDLE SET you just need to put it a little higher like 850.

and just for the record, *I* am a ford tech as well. :Zip2:

lets back up a minute...did you add the mass air sensor and computer to your existing speed density harness, like with a kit? or did you swap the entire harness?

Which computer are you using? Is it still doing the thing where it loses all throttle response and dies if you rev it up with the IAC plugged in? It sure sounds like something is not wired right with the IAC. Does the MAF output stay at .6V when you plug in the IAC or is it throwing it off somehow? I hate diagnosing over the computer.... Sorry I said you were embarrassing me but man, these guys are supposed to ask US the questions. It's a pride thing, you know. What all changed when you put the new MAF on?

oh ok i see.
http://www.stangnet.com/tech/maf/massairconversion.html
it seems our own stangnet has an article on how to do this. there is a wire relating to the fuel pump relay you have to move or you get the code 95.

the only commonality i can see between the IAC and the MAF is that they both share VPWR (12 volts). please measure this wire with various things plugged in and unplugged and tell us what you get.

When you say the IAC is wide open what do you mean? When an IAC is wide open the vehicle idles at like 2500 RPM. Do you mean it is shutting all the way and dying? If it idles higher with the IAC plugged in then the MAF reading should be higher with it plugged in. More air coming in, higher MAF voltage. It kind of sounds like it's flooding out. You can't get PIDS on this car right?