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Chad's '86 to '88 ECU conversion (fixed)


Boosted77.
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Helloo from a long time no see member. Boosted77 here. I needed to use Chad's info recently that has been messed up due to a font error that stems from (i think) when the site was hacked several years ago.

 

http://www.starquest...showtopic=28050

 

Here's the topic with the content fixed so that it can be a little more easy to read:

 

86 TSI: A connector

 

1: IGN - (negative)

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 - (negative)

2: AFS

3: Motor position SW (from A 8)

4: GND

5: Intake temp

6: Coolant temp

7: Idle SW

8: n/c

9: n/c

10: +5 volt power

11: O2 sensor

12: ISC - (in) from B 11

13: Ignitor advance

14: Sensor +5 backup

15: TPS

16: Barometric sensor (New wire run to AFS from '88 ECU)

17: n/c

18: n/c

19: Speed (coil)

20: secondary air (catalyst)

21: Diag. Output

22: control relay (fuel pump)

23: ISC + (out) (from B 9)

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

9: Boost guage

10: Injector 1 (primary)

11: Ignitor signal (from A 12)

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 to DSM AFS:

 

green/red----green/orange

red----green/red

black----green/black

white/black----green/blue

new > A 16 to green/yellow

new > +12 Switched to red

n/c----green/white

 

 

Notes:

 

n/c means no connection

 

>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 < don't mess with this one

 

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

 

 

 

To complete this conversion it would help to look over the '86 and '88 electrical scematics.

 

Lastly to count the pins start from the Large "A" harness and contains the large white wire which is the ignition coil negative (on the front and left of the harness plug while facing down) and count to the right then horseshoe around to the next closest wire on the second row.

 

Enjoy and sticky!

 

Keep it Spooled Starquesters.

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