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1986 to 1988 ECU conversion


Chad
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86 TSI:  “A” connector

 

1: IGN –

2: AFS

3: n/c

4: GND (AFS)

5: Intake temp

6: Coolant temp

7: Idle SW

8: Motor Position SW

9: Pressure to gage

10: +5 volt power

11: O2 sensor

12: Ignitor signal

13: n/c

14: n/c

15: TPS

16: n/c

17: Intake temp (OVCP)

18: n/c

19: speed (coil)

20: n/c

21: Diag. Output

22: control relay (fuel pump)

23: secondary air (for catalyst)

24: pressure solenoid

 

86 TSI “B” connector:

 

1: +12V

2: GND

3: GND

4: EGR

5: IGN (cranking)

6: AC relay

7: +12V

8: Inhibitor

9: ISC + (out)

10: Injector # 1

11: ISC – (in)

12: Injector # 2

13: +12V backup

 

 

 

 

88 TSI “A” connector:

 

-            1: IGN –

-            2: AFS

from A 8      3: Motor position SW

-            4: GND

-            5: Intake temp

-            6: Coolant temp

-            7: Idle SW

n/c            8: n/c      

n/c            9: n/c

-            10: +5 volt power

-            11: O2 sensor

from B 11      12: ISC – (in)

n/c            13: Ignitor advance

n/c            14: Sensor +5 backup

-            15: TPS

new to AFS >      16: Barometric sensor

n/c            17: n/c

n/c            18: n/c

-            19: Speed (coil)

n/c            20: secondary air (catalyst)

-            21: Diag. Output

-            22: control relay (fuel pump)

from B 9      23: ISC + (out)

n/c            24: AC relay

 

88 TSI “B” connector:

 

-            1: +12 V

-            2: GND

-            3: GND

-            4: EGR

-            5: IGN (cranking)

-            6: AC switch

-            7: +12 V

-            8: inhibitor

n/c            9: Boost gage

-            10: Injector 1 (primary)

from A 12      11: Ignitor signal

-            12: injector 2 (secondary)

-            13: +12 V backup

 

since a different MAS is needed to convert, you may as well step up to a 1-G DSM MAS, they are cheaper and work quite a lot better.

 

 

86 AFS:            DSM  AFS:

 

green/red            green/orange

red                  green/red

black                  green/black

white/black            green/blue

new > A 16            green/yellow

new > +12 Switched      red

n/c                  green/white      

 

 

Notes:

 

>”n/c”  means “no connection”

 

>”-“  means “stays the same”

 

>”From A 8”  means “remove from stock 86 connector and relocate to the 88 pin number”

 

>On two pins, you will have to cut the wires and solder on the pin from the “A” or “B” connector, these connectors use different pins, you will have the pins you need when you start to move them.  Some move from “A” to “B”, and some from “B” to “A”.  Some leads may be left over, these are pins not used (if you eliminate the secondary air and the stock boost gage)

 

This conversion also requires an 87/89 ISC assembly.  The new ISC requires a +5 V supply and a ground for the new functions,  because the MPS converted from a simple switch to a potentiometer, you need 2 additional wires.  However, the mitsu engineers decided to add 3 wires instead, and the 3rd is un-used at the ISC end, it is the blue/yellow and literlay has no physical connection at the ISC end, either in the ISC nor in the connector itself so don't bother with it.  

 

looking at the diagrams, it shared the common ECU ground in 87/89's, so ground it anywhere.  same for the +5 V, it connects to a common supply, so just find 5V at the ECU or at some other component like the TPS which is just inches away.

 

 

So here's what you need to do:

 

looking at the 87 ISC, you have a connector that has black/red, black/green and black/blue, this is the motor and idle SW.  It connects as follows to the 86 harness:

 

87 ISC motor :

 

87 ISC black/red       to   87 harness yellow/black  (splice here) to 86 harness  green/white

 

87 ISC black/green    to   87 harness yellow/lbue  (splice here)  to  86 harness black/yellow

 

87 ISC black/blue      to   87 harness yellow/red    (splice here)  to 86 harness yellow/red

 

now you have the 4 pin connector with green/red, blue/red, black, and blue/yellow, this is the new MPS circuit and connects as follows:

 

87 MPS:

 

87 ISC red     to   87 harness green/red    (splice here)   to  new +5 volts  

87 ISC green  to  87 harness blue/red      (splice here)   to  86 harness green/black

87 ISC black  to   87 harness black          (splice here)   to  new ground

 

87 ISC red jumper  to   87 harness blue/yellow   to   N/C  

 

leave the pins at the ECU where they are, they are correct, you simply need to add the 87 ISC, splice the 87 harness to the 86 harness where is says "splice here", and wire in the +5 and the ground

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you just need 2 wires of 14-16 gage and run them from the ECU "B" connector to the MAS, you'l have to poke through the fire wall for that, but there are several places to go though.  If you look on the 86 wiring chart, you can find the nessesary +12 v and ground to use for this DSM MAS.
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Guest Paul87Quest
No it will not work as you need the 87-89 style ISC assembly that has a motor position sensor (the bump on the isc assembly). The ISC should be replaced with the later style to remain trouble free....
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You do have to change the ISC, I updated my instructions in the first posing.  After discussing this with Steve F, we figures it out.  I never noticed the problem on mine since it idles just fine without the ISC  ???
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  • 8 months later...
I take it converting to the '89 ECU should be about the same as the instructions for the 88 ECU or?  I have the '86 Star, an 86 Shop Manual and an '89 ECU but not the '89 manual so a bit difficult for me to cross reference. :-/ :-/  If have the information available, please add to this post.  Thanks....
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88 and 89 ECUs are virtually identical.  You can replace one with the other with absolutely no wiring changes.  So Chad's instructions can be used to swap in an 89 ECU as well.  In fact, the 87 has the same ECU pinout so you could even swap in an 87 ECU although there'd be almost no gain at all - especially for the amount of work involved.

 

Also, in 1987, Mitsu quit using different ECUs for automatic tranny cars vs. 5-speed cars.  The ECU is identical regardless of tranny type.  One of the wiring harness wires tells the ECU what kind of transmission is in the car and the ECU makes the appropriate adjustments.  Thus, when doing Chad's conversion, you can use an 88 or 89 ECU from either a 5-speed or automatic equipped donor car.

 

mike c.

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  • 1 month later...
all so the isc  moter is not wired correctly. i found this out the hard way when i hooked it up and the moter went to 5,000 rpm untill i shut the moter off.  just to let you know. the yellow/blue is the + for the isc motor.the yellow/black is the - for the isc motor. so the yellow/blue needs to go the the green/white, and the yellow/black goes to the black/yellow. i compaired the 86 to the 88 wiring diagram and found this out.
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  • 4 months later...
  • 1 year later...
What hard parts are required for this conversion?  I know I'll need a 88-89 ecu and 87-89 ISC, but what about injectors?  Could I use injectors from a 87-89?

 

Someone please fill me in.

 

Thanks,

Gabe

 

so would this work on a 85.5 esi? if it would id like to do it? and do i need new injectors?

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  • 5 months later...
What hard parts are required for this conversion? I know I'll need a 88-89 ecu and 87-89 ISC, but what about injectors? Could I use injectors from a 87-89?

 

Someone please fill me in.

 

Thanks,

Gabe

 

waiting for reply to this as well.

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  • 1 year later...

FOR FUTURE REFRENCE:

 

the 87 is this: (I'VE NOW ADDED COLORS TO THE CHART) AND EDITED THE DECRIPTIONS FOR THE 87.

 

THESE ARE STRAIGHT OUT OF AN 87 MANUAL.

 

87 TSI “A” connector:

 

W 1: IGN – (coil)

WB 2: AFS

LR 3: Motor position SW

B 4: GND

GR 5: air Intake temp

YG 6: Coolant temp

YR 7: Idle SW

8: n/c

9: n/c

GR 10: +5 volt power

W 11: O2 sensor

YB 12: ISC – (in)

YB 13: Ignitor advance

LY 14: MPS GROUND backup

GW 15: TPS

BW 16: Barometric sensor

17: n/c

18: n/c

LgB 19: Speed (coil)

RG 20: secondary air (catalyst)

BR 21: Diag. Output

WR 22: control relay (fuel pump)

YL 23: ISC + (out)

 

87 TSI “B” connector:

 

R 1: IGN +12 V

B 2: GND

B 3: GND

RW 4: EGR

BY 5: IGN START(cranking)

BW 6: AC switch

R 7: IGN +12 V

BY 8: GROUND

YG 9: Boost gage

YB 10: Injector 1 (primary)

BR 11: Ignitor signal FOR INJECTOR TIMING

YL 12: injector 2 (secondary)

B 13: +12 V CONSTANT

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  • 2 years later...
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