Loose ignition coils (Page 1/2)
freakiero AUG 14, 07:52 PM
Hi,

87 4 cylinder, my ignition coil for cylinders 2 and 3 is loose and I believe it's causing me to misfire under load. Unfortunately, there is no space for me to fit a wrench or a socket and properly tighten these down. Even if I could, the bolts are spinning when I turn the nut. Any suggestions?
Gizmo0816 AUG 14, 10:30 PM
Harbor freight sold some deep well thin wall sockets, its a tight fit, but they worked for me. As for the spinning bolt, if memory serves me right you have 4 bolts that hold your icm/coil packs, those bolts can back out of their recess that they sit in, you'll need to make sure those bolts stay in place while your installing the icm and coil packs.
So my guess is that bolt isn't sitting where it should be and thats why it's spinning.

This is all off memory tho, its been a couple of years since I had to mess with mine.

I believe the link is the set I bought. If it doesn't include the right size, then its not the same set I bought, but I'm pretty sure those nuts are either an 8 or a 10.

https://www.harborfreight.c...-12-piece-57956.html

[This message has been edited by Gizmo0816 (edited 08-14-2025).]

Dennis LaGrua AUG 15, 03:46 AM
I believe those coils should be held in place with a 5.5 MM hex head screw not a stud and nut. They are fastened in place this way on most of the GM cars that I've worked on. If the prior owner changed the mounting method stripped the holding threads you may need to replace the mounting plate.

------------------
" 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 "

[This message has been edited by Dennis LaGrua (edited 08-15-2025).]

82-T/A [At Work] AUG 15, 08:00 AM

quote
Originally posted by Dennis LaGrua:

I believe those coils should be held in place with a 5.5 MM screw not a stud and nut. They are fastened in place this way on most of the GM cars that I've worked on. If the prior owner changed the mounting method stripped the holding threads you may need to replace the mounting plate.





If I'm not mistaken, that whole "pad" comes out, right? It's bolted to the car, and then the two coils bolt to the pad?
Gizmo0816 AUG 15, 12:26 PM

quote
Originally posted by Dennis LaGrua:

I believe those coils should be held in place with a 5.5 MM hex head screw not a stud and nut. They are fastened in place this way on most of the GM cars that I've worked on. If the prior owner changed the mounting method stripped the holding threads you may need to replace the mounting plate.



Whats shown in the picture is the same way mine is setup, so i think that is stock.

[This message has been edited by Gizmo0816 (edited 08-15-2025).]

Gizmo0816 AUG 15, 12:30 PM
It's not the best picture, but this is a photo I took back when I tore mine apart. Its got a stud and a bolt here too.
css9450 AUG 15, 02:21 PM

quote
Originally posted by Gizmo0816:

Its got a stud and a bolt here too.



That's really strange. Who knows, maybe that's what they were using back in the early days of DIS.

All my DIS experience has been on newer cars and like Dennis said, were 5.5 mm or possibly 7 mm (I usually use a nut driver for these). Small bolt, no stud.
Dennis LaGrua AUG 15, 07:18 PM

quote
Originally posted by Gizmo0816:

It's not the best picture, but this is a photo I took back when I tore mine apart. Its got a stud and a bolt here too.



In your picture #1 that shows a gray coil it that looks like there is little room to tighten the nuts that hold the coils in place. Picture number two shows black coils and it looks as though a much smaller fastener was used. If if it is a bolt ,its far smaller that what you show in picture #1. I find it quite unlikely that GM originally mounted those coils with a stud and a nut. Can anyone here who owns an 88 with a stock Duke engine please post pictures of their coil set up.

------------------
" 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 "

freakiero AUG 15, 11:32 PM

quote
Originally posted by 82-T/A [At Work]:
If I'm not mistaken, that whole "pad" comes out, right? It's bolted to the car, and then the two coils bolt to the pad?



Thank you, I didn't realize that at first. There are square holes in the pad which I'm guessing are meant to fit carriage bolts from the factory. The hardware must have changed from a previous owner or at a shop, cause it was a mess. I put in some new nuts and bolts that actually fit and discovered that my crankshaft sensor is roughed up, so looks like that ended up being responsible for my engine problem.

Thank you everyone for the help!
Dennis LaGrua AUG 16, 03:38 AM

quote
Originally posted by freakiero:


Thank you, I didn't realize that at first. There are square holes in the pad which I'm guessing are meant to fit carriage bolts from the factory. The hardware must have changed from a previous owner or at a shop, cause it was a mess. I put in some new nuts and bolts that actually fit and discovered that my crankshaft sensor is roughed up, so looks like that ended up being responsible for my engine problem.

Thank you everyone for the help!



Happy to hear that you solved the problem. As you know the crankshaft position sensor is a very critical part. . Just keep an eye on that part as the aftermarket of off brand Chinese parts can have a high failure rate, some right out of the box. Brands of parts that seem to have higher quality are Delphi, A/C Delco, Bosch, NGK and at times Standard.
------------------
" 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 "

[This message has been edited by Dennis LaGrua (edited 08-26-2025).]