On my third C-4, first LT-1. My first mistake was cleaning engine. I was aware of Opti water problem so I used Brakleen to clean off some crud on front of engine. Big mistake. Took out Opti. Just finished installing new Opti. With new opti car ran fine long enough to allow me to adjust fan control module I had installed. Never took car out of garage. Went to start it yesterday and it was a no start. Ran Diagnostic and found I had a bad Ignition Control Module. Took it off today and found NO dielectric grease between module and heat sink. I don't know if I bought it that way or if Brakleen took it off. Either way, I fried module. I sealed and vented my new Opti in the hope I could clean the engine once in awhile. Unfortunately the geniuses who designed the Opti left the ICM with dielectric grease unprotected. Lesson learned. DON'T CLEAN your LT-X engine

I also found on my 93 that with alternate fan control, code 28 (quad driver) is set, but does not illuminate check engine light. According to manual, ECM monitors fan ground circuit. First time I've run into that. It seems with newer models big brother is watching your every move.

Any thoughts on replacement modules. My thought was to use GM but I see original GM unit was made in Singapore. I found Delco replacement for $80.14 plus shipping. Anyone know of a better unit or price? TIA.

Larry

 

A solvent such as brake cleaner could very well seep and creep and get between the ICM and its heat sink and dissolve the thermal compound. Its not dielectric grease between the ICM and heat sink, its heat sink compound. Don't use dielectric to mount the new ICm or it'll fry on you too. The new module SHOULD come with a small tube of the white heat sink compound in the box. Don't use the thin and runny heat sink compound Radio Shack sells for computer heat sinks, it's not the correct grade for automotive applications.

You can clean the LT1. What you have to do is mist it down with simple green or what works better is Greased Lightning Orange Blast (full strength). But FIRST, take some wash cloth size or hand towel size rags and stuff them on top the opti and around it. Then when rinsing, use a weak stream of water and stay clear of the opti area. I've done this a couple times with safe results.

 

No, stay with the GM part for the ICM. I tried a 3rd party parts store brand ICm and it fecked up the way my LT1 ran. Some other members have tried 3rd party brands with similar results. Seems the LT1 is finicky about what ICM is installed. I know it doesn't make sense, since the 3rd party brands have to be using the same thick film technology but trust me on this one. Stick with the GM ICM.

Try http://www.gmpartsdirect.com for a fair price, They were about $69

 

Like the Vetracr said stick with GM.
I have gone the route and I don't think you want the problems.
Aftermarket will through a check engine light.

 

Isn't Delco still tied very closely to GM? I know they were spun off as a seperate business a few years ago but I can't believe a Delco part wouldn't be the same quality as a Singapore made GM part. After all, when the Opti spark was designed, Delco designed it as GM's electronic division. Am I missing something????

Larry

 

The GM module is manufactured by Delco. The problem with the aftermarket modules is they can not handle the heat produced under the hood. I went through at least 5 aftermarket modules on my LT1 over the course of about 2 weeks. Have been on the Delco for 3 years with no problems. Just be sure to coat the back with the thick white heat sink grease.

 

regarding the code 28 "quad driver module" you should check the "relay looking thingy" on the left inner wheel well just below the ASR. check for loose wires and corrosion on the connections.


Daniel

 

I bought an aftermarket ICM and I now have a check engine light. However my fans stay on all the time now. Are these things related. I do not get a code when I jump the 4/12 pins even though the check engine light is on. It's been a big mystery for a while now.