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The
Backyard Speed Density to
Mass
Air Conversion
The
following was reprinted from
Joe's Mustang EEC-IV Page
courtsey of Cliff Koch
(original
artivicle at http://www.iaw.com/~aubertin/88mgt/eec-iv/sd2maf.htm)
This covers the steps
involved in converting a speed density Mustang to a MAF
Mustang. One thing that should be mentioned is that the
Cobra MAF system is a little different than the GT/LX MAF
system. The Cobra EEC-IV and MAF have been recalibrated
for use with 24# injectors rather than the 19# injectors
that the 'regular' 5.0 EFI engines use. If you are
installing a Cobra system, you should use a Cobra
computer, Cobra MAF, and 24# injectors.
It is strongly
recommended that all connections are soldered. Any sort
of crimp only terminals are only asking for reliability
problems down the road that will be very tough to
troubleshoot.
Parts needed:
Mass Air Flow meter: Get a MAF calibrated for the
injector size you are using. If you are using an
aftermarket recalibrated MAF and are also installing
larger injectors, keep in mind this can cause problems
with ignition timing (leading to part throttle
detonation) along with some drivability problems.
MAF mounting hardware: MAF bracket,
3 MAF mounting screws, and 2 sheet metal screws to mount
the bracket to the shock tower.
MAF power/signal harness: This is
the MAF connector, 4 wires that go to the EEC computer,
and EEC-IV connector pins for two of the wires.
MAF Air tubes: These are the tubes
which go between MAF meter and engine and MAF meter and
air filter box plus the clamps.
(Optional): Three EEC-IV pins and
wire to hook up VSS and FPM2 signals.
| Step 1 |
Removing the speed
density computer
Remove the battery ground cable. Remove the
passenger kick panel. You will probably need to
remove the lower door strip to get the kick panel
out. The kick panel is held on by a screw towards
the back and a 'mushroom' fastener towards the
front. Remove the EEC-IV retaining screw to the
lower right of the computer. Remove the EEC
connector using a 10mm wrench. Clear any
wires/relays out of the way and slide the
computer out.
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| Step 2 |
Install the Mass Air
Flow meter
Remove the air snorkel and the air filter box
cover. Attach the MAF mounting bracket to the
shock tower. I recommend attaching the snorkel
and bracket to the MAF and looking for the
correct holes in the shock tower to use (they
will already be there on many vehicles. Once
found, attach MAF bracket to shock tower and the
MAF to the bracket.
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| Step 3 |
MAF wiring
There are 4 wires that need to be run to the MAF,
2 signal wires and 2 power wires. If you do not
have a prefabricated harness, you will have to
come up with the MAF connector and two pins for
the EEC-IV connector. The MAF can have two types
of connectors on it, a 4 pin or a 5 pin
connector. The pins are marked A B C D (E) on the
MAF sensor. The chart below shows what wire needs
to be connected to which pin number on the EEC
connector:
| 4 pin |
|
5 pin |
|
| MAF |
EEC-IV |
MAF |
EEC-IV |
| A |
37 (power) |
A |
37 (power) |
| B |
40 or 60 (ground) |
B |
No connection |
| C |
9 (signal return) |
C |
40 or 60 (ground) |
| D |
50 (signal) |
D |
9 (signal return) |
| |
|
E |
50 (signal) |
Get the
wires through the firewall via your favorite
method. Mine was to slit the large rubber grommet
that the EEC wiring goes through and push the
wires through that. The power and ground signals
will need to be tapped into the wires currently
going to the EEC connector. It's easier to work
on the wires if they are removed from the
connector. To do this, you first have to remove
the red locking bar on the front of the
connector. The pins are then retained by a small
tab which can be disengaged individually with a
jewelers screwdrive or a paperclip. The signal
wires will need to have EEC-IV type pins soldered
to them and be inserted into the proper locations
in the connector. The locations should be empty.
Check your connections. If these are hooked up
incorrectly, you will likely blow the electronics
in the MAF and could also damage the computer.
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| Step 4 |
Thermactor pump
wiring
The EEC connector positions that control
thermactor valve operations are different between
Speed Density and MAF computers. The wire
currently in position 51 should be moved to
position 38. The wire currently in position 11
should be moved to position 32. You may have to
splice in some extra wire for the pins to reach
the new locations.
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| Step 5 |
Hooking up Vehical
Speed Sensor (VSS) wires
There is a differential signal called VSS
(Vehicle Speed Sensor) which comes from a small
sensor on the transmission where the speedometer
cable is connected. In 1986-1988 MAP cars this
signal was used only by the cruise control and
the sensor may not be installed if your car does
not have cruise control. In MAF cars, this signal
is used by both the cruise control and the
EEC-IV. The wires/pins for these signals are not
physically equipped in a MAP car's wiring
harness, which will yield an error code for NO
VSS SIGNAL- (code 29) from the continuous memory
codes in the EEC-IV. These signals are not
absolutely needed, though some people have
reported stalling when coasting to a stop without
them. You can hook the VSS signals up to the
EEC-IV connector by connecting the input pins of
the EEC to the appropriate wires on the cruise
control module (located just to the left of the
clutch/brake pedals). You need to hook the dark
green/white wire going to the speed control to
pin 3 of the EEC, and the orange/yellow wire to
pin 6 (these are the colors for an '88, anyway).
These positions on the EEC connector are empty
and will require 2 EEC-IV connector pins.
|
| Step 6 |
Hooking up the FPM2
signal
There is a another signal called the FPM2
(Secondary Fuel Pump Monitoring signal). This
signal monitors the voltage going to the fuel
pump, essentially testing whether or not the fuel
pump relay (located under the drivers seat) is
operating correctly. Again, this wire is not in
the harness. This shouldn't cause any problems,
other than having code 95 generated in the EEC-IV
self tests. Again, this wire can be connected to
get rid of the error code. Connecting pin 19 of
the EEC-IV connector to the output of the fuel
pump relay located under the drivers seat
(pink/black wire) will fix the problem. To really
do this correctly, a wire should be run to the
back of the car to tie in after the collision
fuel cutoff switch, but that's a lot of work for
a fairly useless test.
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| Step 7 |
Adding a "Check
Engine" light
Another difference between the speed density and
MAF cars is that MAF cars have a "Check
Engine" light in the dash to alert you to
possible serious problems and it makes reading
out self test codes much easier. The MAF cars
have the "Check Engine" light located
in the light panel on the lower right of the
instrument cluster. Speed density cars don't have
this window, but there is a "Check
Engine" position for a light in the
tachometer face, though there is no bulb
installed. The wire from the EEC to the bulb (via
the flex connector) is also missing. In the '88 harness (not sure of
other years), there is a tan and a black/blue
wire connecting up to the 'Check Engine' circuit
on the instrument cluster flex circuit. For MAF
models, the tan wire hooks to the EEC STO/MIL
line and the black/blue is for the lamp test out
when you start the car. I don't know what these
are connected to in an '88, but the test out
feature does not work, and the STO/MIL line at
the EEC-IV and self test connector is
yellow/black. The wires connected to the check
engine lamp probably end at some open connector
somewhere, but I couldn't track it down, so I cut
the tan and black/blue wires off the flex
connector and ran a new wire to the STO/MIL wire
on the self test connector under the hood (you
could also tap in by the EEC-IV, but it was
easier for me to go through the firewall. You can
get a bulb socket from the HELP! rack at the
local parts store, put in a N194 bulb, and voila,
you now have a working check engine light.
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| Step 8 |
Install MAF computer
Put the locking bar back on the EEC connector if
you haven't already done so. Reinstall EEC-IV and
reconnect the connector.
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| Step 9 |
Attach Hoses to MAF
Attach the hose to connect the MAF to the engine
throttle body and the hose that connects the MAF
to the air filter box cover and tighten the
clamps.
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| Step 10 |
MAP sensor
modification
Disconnect the vacuum hose going to the Manifold
Absolute Pressure sensor located on the firewall
on the upper drivers side. Leave the vacuum port
on the sensor open and plug the vacuum line from
the engine. Do *not* disconnect the electrical
connector from the sensor.
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| Step 11 |
You're done!
Check that everything is back in place and
connected well, reconnect the battery and start
the car. It is normal for the car to idle a
little rough and you may feel some slight surging
when driving until the computer relearns the fuel
curves. A few hours of normal stop and go driving
will usually be enough. If the engine has extreme
idle problems, then something is probably wrong.
Check the wiring from the MAF to the computer.
Try to run KOEO and KOER tests and see what the
problems are.
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The
following was reprinted from
Joe's Mustang EEC-IV Page
courtsey of Cliff Koch
(original
artivicle at http://www.iaw.com/~aubertin/88mgt/eec-iv/sd2maf.htm)
The Corral: Late Model
Mustang Web
Images
and text © Copyright 1998 The Corral.
All Rights Reserved, Duplication Strictly Prohibited.
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