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View Full Version : 84 GN Ignition Control Module Swap/Mod to 86/87


GN_Guy
05-09-2008, 01:25 AM
I recently found my #3-#6 coil had an open in it (no continuity). So, I had to replace the coil pack. Sounds pretty easy, right!?!?

If you have never tried to find one of these - don't waste your time becasue if you find one - you won't want to pay the price. I actually priced the ICM and Coil for the 84/85 GN in 1993-94 and it was amost $200 for the coil and $616 for the ICM!!!! Wonder what they go for now as NOS???

So - taking the advice from the great folks on this message forum, I put the newer 86/87 ICM and Coil into my 84 GN. It's VERY easy - for a price. Put another way - you can take your time and do it pretty inexpensively $50-$100, or you can pay the $200 and do it in under an hour.

Here's what you need:
Coil pack
ICM
Adapter Plate
Harness Adapter

I purchased the adapter plate and harness adapter from Casper's Electronics --> http://www.casperselectronics.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=CEI&Category_Code=8485PERFO . Total for these two parts ~$115. The adapter plate was ~$35 and the harness adapter ~$60. The balance was taxes and shipping. Both parts are of very good quality.

I got my ICM/Coil (they all sell them as a single unit) from a boneyard for $50. Mine came out of a 1986 Olds 88.
This link has a list of all compatible ICM/Coils --> http://www.gnttype.org/techarea/ignition/type2coils.html

Installation is almost idiot-proof. Here are the steps I took:
1. Disconnect the battery.
2. Removed the MAF, top of air filter unit, and ductwork to the throttlebody.
3. Mark and pull the plug wires.
4. Remove the wiring harnesses that are held up off the bottom of the ICM/Coil bracket (3 places) and remove the ICM connector.
5. Remove the ICM/Coil and bracket as one piece - it takes 1 bolt and 2 nuts (bolt is near top of water pump hosing, one nut off of stud in the intake manifold behind ICM/Coil, and one nut off of lower exhaust manifold on front drivers side).
6. Remove the stock ICM/Coil from the bracket.
7. Put adapter plate onto the new/used 86/87 version of ICM/Coil.
8. Put the new (86/87 version) of ICM/Coil and adapter plate onto bracket.
9. Put harness adapter onto the car's ICM connector.
10. Do the reverse of steps 5., then 4., 3., 2. and 1.

LOWER COST ALTERNATIVES:
(But it's the standard time .vs. money thing.)

1. I did my swap in literally less than 50 minutes (not including the time to get the parts together)! I could have made the adapter plate and saved $35, but it would not have looked as good as the unit from Casper's and I would have spent at least 2 hrs or more cutting, drilling, filing, painting, etc., etc.

2. You can change the pin-out on your car's wiring harness by following the technique in this article -->http://www.gnttype.org/techarea/ignition/module.html (http://)
But, for a little over $60 go with the harness adapter - it's too easy.

I hope this saves you some research time in case you find yourself with a bad ICM or Coil in an 84/85 GN. Have fun.