I am still very new to the fiero as a car.

So i have swaped an 87 engine to a manual 5 speed 88.

What i am very curious to is if an 88 engine wire harness will work with an 87 engine?

Secondly, will the 88 computer work with an 87 engine?

4cly or V6?

V6 2.8L

Yes.

They are the same.

Did you use the 87 flywheel on the 87 engine?

[This message has been edited by olejoedad (edited 03-09-2025).]

Thank you!!

Did you use the 87 flywheel on the 87 engine?

i did indeed.

That's good, the two engines are balanced differently.

The cooling system hoses are routed differently as well, it's easy to convert.

[This message has been edited by olejoedad (edited 03-09-2025).]

i did not know that the coolent hoses where routed diffrently.

is there a video or instructions online on how to re rought them?
(i am keeping everything in my 88 GT exeptfor the engine. it is also a 5-speed manuel)

thank you for the heads-up!!

I'd like to point out that while the 85-88 V6 wiring harnesses are essentially the same , the manual harness will not work on an automatic without turning on the feature flag in the chip that instructs the ECM program to lock up the torque converter when required. If the haness and ECM are swapped together then no chip reprogramming is required.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Great point!

I am keeping the computer and the harness from the manuel 88 so that sould be good if you are correct.
( I am assuming you are)

I may have spoken incorrectly about the cooling system routing.

The heater core water returns to the passenger side cooling pipe in both years.

The heater core feed may be different.

Examine the water pumps, the 87 may have a tube where the 88 has a plug in that location.
I will check my Factory Service manuals and get back to you.

You should plan to swap the accessories (at least the alternator) as I think it is different.

88 Y-pipe has better heat shielding and should be swapped over (along with the rest of the exhaust).

In 88 they did away with the cooling blower for the alternator and ignition coil, and the 2 changes above were to facilitate that change.

quote Originally posted by olejoedad: I may have spoken incorrectly about the cooling system routing. The heater core water returns to the passenger side cooling pipe in both years. The heater core feed may be different. Examine the water pumps, the 87 may have a tube where the 88 has a plug in that location. I will check my Factory Service manuals and get back to you.

The 87 feeds the heater core from the thermostat housing.

quote Originally posted by I Lean: The 87 feeds the heater core from the thermostat housing.

So does the 88.

To the original poster....

Both model years return the heater core flow to the passenger side undercar coolant tube.

There is NO DIFFERENCE in cooling system layout.

88 alternator plug will be slightly different. You can keep 87 alternator and splice in correct pigtail, or upgrade to better 88 only alternator.

quote Originally posted by GodSend: 88 alternator plug will be slightly different. You can keep 87 alternator and splice in correct pigtail, or upgrade to better 88 only alternator.

And if you want to buy one, Rodney Dickman sells an adaptor for $15 bucks here: https://rodneydickman.com/p....php?products_id=361

So if i kept the 87 alternator, then i would need to buy an adapter for the 88 wireing harness?

quote Originally posted by the_snowman: So if i kept the 87 alternator, then i would need to buy an adapter for the 88 wireing harness?

Or, you could
1. Wire in the plug from the 87 harness. (It's only 2 wires, just match the colors)
2. Use the 88 alternator ( it's a better alternator, and your best choice)

The two differences in the 87 and 88 engine harnesses that come to mind are the alternator and oil pressure sending unit. Each can be changed out to match the harness.

If the O/P transfers accessories from the 88 engine to the 87 engine, no wiring harness changes are needed.