Toyota MR2 Message Board - View Single Post - 1986 Mk1 4A-GE to GZE Engine Swap (56k Beware, Lots Of Pics)

TheAmazingDave · 01-02-2006, 01:38 PM

OK, I'm proud to say that as of yesterday evening, the swap is complete and the engine runs like nobody's business! This will be my final write-up to finish this up.

I spent the whole weekend working on the wiring harness. At about 8:00 Sunday evening, I got all the wiring gremlins worked out with the help of a fellow board member's write-up found HERE and the car was ready for final assembly starting early Monday morning. This pic shows the harness in the cabin, no changes were made to any of this:

You can see some long stray wires coming from the kick panel fuse area. These are wires left from the old aftermarket alarm which is long gone. I ended up cutting out these wires and using them to extend the wires for my O2 sensor. I also took the starter main feed wire out of the 86's harness as it was longer to reach the starter in the back, and I used heavy 10 gauge wire to extend the starter's solenoid power. You DO NOT need to extend these wires if you have a C-52 with the starter mount under the intake and use the SC's exhaust system pieces. My C-50 transmission has the starter mount under the exhaust manifold where stock auto GZE's had it under the intake. That's why those wires were extended. And I had to extend the O2 wires because I kept my 86 exhaust system, which mounts the O2 at the bottom of the manifold, as opposed to the GZE's stock system which placed it right before the flex pipe.
Below you see the modifications to the 86's body harness. There were some big changes that were explained in the procedure I posted a few lines above. Note that there were many wiring harness changes over the years, and even several for the same model years. His write-up did not work 100% for me, but it put me pretty damn close. I had to figure the starter circuit out for myself, but everything else was spot on according to the write-up.

The few stray wires you see are for a few accessories like the octane selector switch (Red Wire), the SC on indicator light (Yellow Wire), and for the center high mounted stop light (Yellow with Red Stripe).

In the above pic, you can see the 3 wires I had to add. The black wire runs from the ECU to the Check Engine light, the green one is for the engine bay cooling fan, and the red one controls the injector relay, and had to be spliced into the wires for the injector relay's pin 4.

Here is all the modules and the ECU plugged in inside the trunk. You can't see the voltage regulator, cooling fan computer, or speed controller (cruise control controller) in this pic, but they're there. The green box is the 86's speed controller. i used the 88's which is a lighter shade of green, just out of the picture. The modules still need to be mounted to the rear firewall. I might take care of that tomorrow.

(Edited to fix broken link)

01-02-2006, 01:38 PM	#9 (permalink)
TheAmazingDave Cage Fighter Join Date: Mar 2005 Location: San Jose, CA Posts: 1,112 Thanks: 13 Thanked 7 Times in 7 Posts My Google Map iTrader Rating: (0/0% )	OK, I'm proud to say that as of yesterday evening, the swap is complete and the engine runs like nobody's business! This will be my final write-up to finish this up. I spent the whole weekend working on the wiring harness. At about 8:00 Sunday evening, I got all the wiring gremlins worked out with the help of a fellow board member's write-up found HERE and the car was ready for final assembly starting early Monday morning. This pic shows the harness in the cabin, no changes were made to any of this: You can see some long stray wires coming from the kick panel fuse area. These are wires left from the old aftermarket alarm which is long gone. I ended up cutting out these wires and using them to extend the wires for my O2 sensor. I also took the starter main feed wire out of the 86's harness as it was longer to reach the starter in the back, and I used heavy 10 gauge wire to extend the starter's solenoid power. You DO NOT need to extend these wires if you have a C-52 with the starter mount under the intake and use the SC's exhaust system pieces. My C-50 transmission has the starter mount under the exhaust manifold where stock auto GZE's had it under the intake. That's why those wires were extended. And I had to extend the O2 wires because I kept my 86 exhaust system, which mounts the O2 at the bottom of the manifold, as opposed to the GZE's stock system which placed it right before the flex pipe. Below you see the modifications to the 86's body harness. There were some big changes that were explained in the procedure I posted a few lines above. Note that there were many wiring harness changes over the years, and even several for the same model years. His write-up did not work 100% for me, but it put me pretty damn close. I had to figure the starter circuit out for myself, but everything else was spot on according to the write-up. The few stray wires you see are for a few accessories like the octane selector switch (Red Wire), the SC on indicator light (Yellow Wire), and for the center high mounted stop light (Yellow with Red Stripe). In the above pic, you can see the 3 wires I had to add. The black wire runs from the ECU to the Check Engine light, the green one is for the engine bay cooling fan, and the red one controls the injector relay, and had to be spliced into the wires for the injector relay's pin 4. Here is all the modules and the ECU plugged in inside the trunk. You can't see the voltage regulator, cooling fan computer, or speed controller (cruise control controller) in this pic, but they're there. The green box is the 86's speed controller. i used the 88's which is a lighter shade of green, just out of the picture. The modules still need to be mounted to the rear firewall. I might take care of that tomorrow. (Edited to fix broken link)