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95 LT1 Ran rough, misfired, and exhaust backfired. Replaced opti but it didn't start. Found out it can be installed wrong, even if it goes on easy. Re installed it. It now starts but misfires and stalls out, It will sometimes stay running on idle but it usually will die or will die as soon as i put it in gear. I can keep it running if i keep on the gas but it will misfire hard and run really rough and if really give it some gas it will backfire out exhaust. It has new wires, new plugs, new icm, new coil, new opti, new water pump, 40 psi fuel pressure, a small vacuum leak but I temporary repaired it (waiting for new silicon lines to come in). I am Lost as what it could be.
 

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Check coolant temperature sensor pig tail for corrosion. I had same symptoms and found corrosion on sensor inside of block (lower right side as you view engine from front of car) and the sensor that goes into water pump had corrosion on sensor. Mine would be rough to start, idle rough, stall when I hit gas or sometimes not start. Also when it ran, black smoke out of exhaust. Getting new sensors and pigtails solved my problems on ‘95 LT1


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When you installed the spark plug wires, did you route them to the correct cylinders? I ask because an opti doesn't have the normal plug wire line up like most cars have.

Go to the shoebox site at the following link. He has opti pin drive installation pic. And plug wire routing. www.shbox.com

opti installation pic #54 in component views section.
plug wire position on cap #9 in electrical section & #15 in reference area

And do yourself a favor and download the 95 factory service manual at the following link. www.mediafire.com/?40mfgeoe4ctti
 

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When you installed the spark plug wires, did you route them to the correct cylinders? I ask because an opti doesn't have the normal plug wire line up like most cars have.

Go to the shoebox site at the following link. He has opti pin drive installation pic. And plug wire routing. www.shbox.com

opti installation pic #54 in component views section.
plug wire position on cap #9 in electrical section & #15 in reference area

And do yourself a favor and download the 95 factory service manual at the following link. www.mediafire.com/?40mfgeoe4ctti
That's the exact diagrams I followed. Triple checked them. All correct.
 

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When you installed the spark plug wires, did you route them to the correct cylinders? I ask because an opti doesn't have the normal plug wire line up like most cars have.

Go to the shoebox site at the following link. He has opti pin drive installation pic. And plug wire routing. www.shbox.com

opti installation pic #54 in component views section.
plug wire position on cap #9 in electrical section & #15 in reference area

And do yourself a favor and download the 95 factory service manual at the following link. www.mediafire.com/?40mfgeoe4ctti
Check coolant temperature sensor pig tail for corrosion. I had same symptoms and found corrosion on sensor inside of block (lower right side as you view engine from front of car) and the sensor that goes into water pump had corrosion on sensor. Mine would be rough to start, idle rough, stall when I hit gas or sometimes not start. Also when it ran, black smoke out of exhaust. Getting new sensors and pigtails solved my problems on ‘95 LT1


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I replaced the coolant temp sensor about a year ago. But I will check again as I have no more leads and am tired of running in circles with the opti.
 

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Pull both those sensor pigtails; that’s where I had a lot of corrosion due to humidity down here in the south. I was amazed that could cause the car to run so badly. But it all goes into algorithm used by computer.


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Also, I would buy new sensor ahead of time because when you pull it from side of block you will start draining coolant right away unless you put your finer over hole. Definitely make sure engine is cool


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What brand of opti did you buy? If it's a parts store, or ebay opti, it is China junk.

Only good optis are the rebuilt GM, Delco, & delphi, ones. There are no new ones left from these brands.

I've heard of a company called Petris that remanufactured optis with a Mitsubishi grade optical sensor. Don't know anyone who has one, however.

If you plan on living with your lt1 car, you should invest $70 on a PC based oscilloscope. The scope is only 100% way of testing opti low & high resolution signals.

Have you checked for codes with an obd 1 scanner? Opti codes dtc 16 & 36 plus icm codes dtc 41 & 42 do not turn on the check engine light.
 

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What brand of opti did you buy? If it's a parts store, or ebay opti, it is China junk.

Only good optis are the rebuilt GM, Delco, & delphi, ones. There are no new ones left from these brands.

I've heard of a company called Petris that remanufactured optis with a Mitsubishi grade optical sensor. Don't know anyone who has one, however.

If you plan on living with your lt1 car, you should invest $70 on a PC based oscilloscope. The scope is only 100% way of testing opti low & high resolution signals.

Have you checked for codes with an obd 1 scanner? Opti codes dtc 16 & 36 plus icm codes dtc 41 & 42 do not turn on the check engine light.
I got a petris opti. and I scanned it with a snap on soulus and no codes.
 

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Something you need to know about the low & high resolution codes is; if both low & high resolution pulses are missing, no code will set.

Another reason all lt1 owners should have an oscilloscope.
 

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Something you need to know about the low & high resolution codes is; if both low & high resolution pulses are missing, no code will set.

Another reason all lt1 owners should have an oscilloscope.
Do you have a link, or know where I can buy one of those smart phone oscilloscope attachments ?
I’m not currently having any problems with my opti but I’d still like to have one on hand to check them with.
Thank You for any information you can supply.
 

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You can search Ebay. Use smart phone oscilloscope as your search. I recently searched Ebay and found they had PC based scopes, hand held scopes, and scopes you add to your smart phone.

Unfortunately, the only type that I have used, and can say works well, is the PC based scope. But the hand held & smart phone add on scopes were cheap enough to take a chance.
 

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Check coolant temperature sensor pig tail for corrosion. I had same symptoms and found corrosion on sensor inside of block (lower right side as you view engine from front of car) and the sensor that goes into water pump had corrosion on sensor. Mine would be rough to start, idle rough, stall when I hit gas or sometimes not start. Also when it ran, black smoke out of exhaust. Getting new sensors and pigtails solved my problems on ‘95 LT1


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Will definitely check the coolant temp sensor for the incoming LT1 project. We'll just finish installing the suspension kit and xd wheels on the truck and clear the garage before we can take a closer look. The owner mentioned his son probably messed it after having some rough idle issues.
 
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