LT1-LT4 Modifications 1993-97 Gen II Small Block V8

No Start, likely coil, optispark, or ICM. SOLVED

Thread Tools
 
Search this Thread
 
Old Aug 5, 2016 | 01:59 PM
  #1  
ThatDudeOrion's Avatar
Thread Starter
Teching In
 
Joined: Feb 2012
Posts: 19
Likes: 0
Default No Start, likely coil, optispark, or ICM. SOLVED

Hi all, I had an eventful day yesterday and wanted to share the tale for the benefit of the forum.

TL;DR: the pink wire in the black coil connector was intermittently supplying the necessary switched 12v power the coil needed resulting in stalling, hard start, and subsequently no start conditions. Made jumper wire from fuse block to coil, car ran great.

Bought second hand MSD coil and 6A box with harness off member of another forum

Installed coil only first. Briefly started car up to ensure functionality, started and ran fine with MSD Coil, original 175k opti and ICM, went to bed.

Car started ran and drove fine until I was about 15 miles from home when it died during coast down to a stoplight, got it refired, died again short distance later. Much trouble getting it started again, seemed like classic ICM failure, ***** out once engine is warmed up (throwing no codes). Got the idea to disconnect MAF to put the car into OLSD/Limp Home mode. Started and idled like a champ...hmmmm.

Made it another 2 miles and died while making a U-turn to go home and not get stranded out on the road when I realized that I hadn't fixed anything by disconnecting MAF, would crank but not refire.

eventually had somebody pick me up and I went home to grab tools and parts store to get ICM because I was SURE that's what the problem was.

Swapped ICM, still no start, ****...Start going through the opti checklist with my multimeter. All 4 pins on ICM connector are doing what they're supposed to, all 3 on the coil connector are as well, I didn't think it was PCM because I was reading and flashing it, so I was starting to lose hope that it was maybe the opti and I was going to need a tow since I didn't feel comfortable doing that in a random roadside parking lot.

Decided to try to eliminate ALL doubt before wasting money on an opti I didn't need, like I had with the ICM. So I check the resistance of the new to me MSD coil, around 5K, good, OEM was like 8k when I checked it. Opti Harness resistance values were ~1-2.2k on all pins. I swapped the OEM coil back in just to be sure, no change....Its gotta be the opti...but it still didn't feel quite right as it was throwing no codes and I knew the injectors were firing while cranking because of the stroooong smell of gas from the intake.

So I ran through the checklist again and wouldn't you know it, the pink wire in the black coil connector (only wire in that connector on my car(95)) was now NOT showing 12v switched like it was when I went through the checklist the first time. It was not shorted to ground, and it had continuity with the #11 fuse (IGN) on the fuse block, but it was not transmitting power, at least not consistently. So my theory is that there was an incomplete/partial break in the copper in that wire, so I made a jumper to go directly from the fuse block to the coil to provide it the 12v switched that should have been on that wire, and the car started right up and I was able to drive home.


This was a failure that I haven't really seen before and maybe this info can help some people keep from throwing money at the problem with new optis, coils, and ICM's
Reply




All times are GMT -5. The time now is 06:10 AM.

story-0
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

Slideshow: We take a close look at the ONE and Artidiag 800BT2 diagnostic tools from Topdon and the reasons to buy one over the other.

By Pouria Savadkouei | 2026-05-28 11:05:11


VIEW MORE
story-1
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.

By Verdad Gallardo | 2026-05-26 18:23:54


VIEW MORE
story-2
7 Most Reliable High-Performance Engines GM Has Ever Built

Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.

By Verdad Gallardo | 2026-05-21 16:45:27


VIEW MORE
story-3
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-4
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-5
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-6
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-7
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-8
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-9
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE