opti again! or is it?
Thread Starter
Racer
Joined: Mar 2002
Posts: 312
Likes: 6
From: Troy Al
opti again! or is it?
I’ve changed the opti on my 93 coupe too many times to count. I lost count, but at least 5 times. The past 4-5 times I drove the car, it was hard to crank cold. Progressively getting harder and harder. The last few times it would crank after a shot of either down the throttle body, but not any more. During these time it ran fine after it ran a little and warmed up.
The last go ‘round I put a new AC Delco distributor, MSD cap and rotor w/ the venting option. Also a new MSD blaster coil. I plan to first check all plug wires. Go back to the stock coil. Look for the +5 control voltage on the white wire. If none of this helps, I’m thinking rotor button. Maybe it came loose. Any thoughts?
I thought I'd get at least 100 miles this time.What a poor design!
The last go ‘round I put a new AC Delco distributor, MSD cap and rotor w/ the venting option. Also a new MSD blaster coil. I plan to first check all plug wires. Go back to the stock coil. Look for the +5 control voltage on the white wire. If none of this helps, I’m thinking rotor button. Maybe it came loose. Any thoughts?
I thought I'd get at least 100 miles this time.What a poor design!
Instructor
Joined: Sep 2004
Posts: 208
Likes: 1
From: Lawrenceville GA
Back when I got paid to turn wrenches....any time a gmc product had a no start I changed the control module. Use to be in the dist. but yours is on the head with the coil. Checked the harness to the opti?
I've also had the computers rebuilt and now keep a spare. More answers will follow I'm sure.
Please post the final result!
I've also had the computers rebuilt and now keep a spare. More answers will follow I'm sure.
Please post the final result!
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Hard to crank and hard to start are two different things. Is the car hard to start or crank? Cranking is just turning the engine over with the starter, is this ok?
It is is trying to start after shooting ether down the TB, then you might want to check fuel pressure.
FYI, Ether is really bad for your engine, use at your own risk.
Also, have you checked spark at the plugs during cranking?
It is is trying to start after shooting ether down the TB, then you might want to check fuel pressure.
FYI, Ether is really bad for your engine, use at your own risk.
Also, have you checked spark at the plugs during cranking?
Thread Starter
Racer
Joined: Mar 2002
Posts: 312
Likes: 6
From: Troy Al
The engine spins over, but no ignition. New Fuel pump very recently. I did buy a fuel press, guage a while back, I can check again.
I hear what you're saying Nathan. Had the same thought. It will run for a while after changing the opti. Then quit. Question is. If not the opti. What is it?
I hear what you're saying Nathan. Had the same thought. It will run for a while after changing the opti. Then quit. Question is. If not the opti. What is it?
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
The engine spins over, but no ignition. New Fuel pump very recently. I did buy a fuel press, guage a while back, I can check again.
I hear what you're saying Nathan. Had the same thought. It will run for a while after changing the opti. Then quit. Question is. If not the opti. What is it?
I hear what you're saying Nathan. Had the same thought. It will run for a while after changing the opti. Then quit. Question is. If not the opti. What is it?
I would verify that fuel pressure, make sure it is not leaking down after you shut off the key.
Get a cheap 5 dollar spark tester at Harbor Freight. When the car is hard to start like this, see if you have spark.
Do you have a FSM?
Thread Starter
Racer
Joined: Mar 2002
Posts: 312
Likes: 6
From: Troy Al
It could be a LOT of things. Cars are just a bit complex but they are not rockets.
I would verify that fuel pressure, make sure it is not leaking down after you shut off the key.
Get a cheap 5 dollar spark tester at Harbor Freight. When the car is hard to start like this, see if you have spark.
Do you have a FSM?
I would verify that fuel pressure, make sure it is not leaking down after you shut off the key.
Get a cheap 5 dollar spark tester at Harbor Freight. When the car is hard to start like this, see if you have spark.
Do you have a FSM?
In the past, when the opti went out. Code 36, one day it spins over, but never starts. Other times, same thing with no codes.
I think I'll drive it around some. Replace the harness when it comes in, maybe go back to the stock coil.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Sounds like a flaky ignition control module to me, I have seen them have temperature related problems, which could explain your seemingly completely erratic results.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Sounds like a flaky ignition control module to me, I have seen them have temperature related problems, which could explain your seemingly completely erratic results.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
My 92 would stop running everytime it got hot on the road course. I mean frustrating when you can only run 10 or 15 min.Flat tow anytime ther was a red flag.
One other thing to check - what wound up to really fix mine - is check the wiring from the opti to the ECM connector on the passenger side.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Sounds like a flaky ignition control module to me, I have seen them have temperature related problems, which could explain your seemingly completely erratic results.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
Trouble is there isn't a good way to test that. Sure the parts stores will tell you they can test it, but if it's an intermittent problem, their test will likely show good even if the unit is faulty.
When I had one fail I was fortunate enough to be able to borrow one to test with. Once I verified it solved my problem, I bought it from the guy. The module on mine is actually off of a 96 F-body I believe.
Only does it from cold/warm to hot starts. Only when it wants too, sometimes it is ok. It is mis-firing at idle, at above 190 or so. Will not restart hot/warm must cool down. Tries to but will not. I'm losing spark for sure but I want to run the test on 6E3-C4-5 of the FSM, to verify what I have, for sure.
Problem is the lack of assistant and intermittent nature. Then again I don't have to drive the car (snow on the ground).
If you have a FSM run thru this test.
Thread Starter
Racer
Joined: Mar 2002
Posts: 312
Likes: 6
From: Troy Al
I'm battling what I think is a ICM, right now. Trying to catch it in the act, very intermittent. When I do catch it I never have an assistant around to crank while I watch/do tests.
Only does it from cold/warm to hot starts. Only when it wants too, sometimes it is ok. It is mis-firing at idle, at above 190 or so. Will not restart hot/warm must cool down. Tries to but will not. I'm losing spark for sure but I want to run the test on 6E3-C4-5 of the FSM, to verify what I have, for sure.
Problem is the lack of assistant and intermittent nature. Then again I don't have to drive the car (snow on the ground).
If you have a FSM run thru this test.
Only does it from cold/warm to hot starts. Only when it wants too, sometimes it is ok. It is mis-firing at idle, at above 190 or so. Will not restart hot/warm must cool down. Tries to but will not. I'm losing spark for sure but I want to run the test on 6E3-C4-5 of the FSM, to verify what I have, for sure.
Problem is the lack of assistant and intermittent nature. Then again I don't have to drive the car (snow on the ground).
If you have a FSM run thru this test.
In electronics we use "cool spray" in a can, will rapidly cool down anything. Perhaps I may try that on my ICM.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
I have a long jumper wire from the small wire on the starter. I turn the key on, then tap that wire to the positive post of the Alt. (12+dc) to engage the starter from under the hood.
In electronics we use "cool spray" in a can, will rapidly cool down anything. Perhaps I may try that on my ICM.
In electronics we use "cool spray" in a can, will rapidly cool down anything. Perhaps I may try that on my ICM.
Cool in a can idea is a good one. I had that idea too, but I don't know where to find that stuff.