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93 trans am LT1 wont start has power to goodcoil no spark coming out

4447 Views 6 Replies 4 Participants Last post by  nick21.2011
hi there i need help, my 93 trans am lt1 wont start, it turns over and has power to the coil but no spark coming out to optispark, and i know its a good coil and module cuz i took it off a running lt1. what could this be??
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I suggest reading the codes. The 3 ignition biggies dtc 16 , 41 , & 42 don't light the check engine light. But any of the 3 will cause a no spark condition.

You need to give us some history of your problem. Is this something that just started? Is the no spark condition been happening for a while? What testing have you done?

We have the 93 factory service manual in the 4th gen tech section to download. It has a driveability & emissions section with troubleshooting, explanations of the codes. Also an electrical section with wiring diagrams, component views, etc.

Did I mention you can read the codes on a 93 by shorting the dlc pins with a paperclip. Connect pins A & B together. You can find a pic of dlc at shoebox's site. It's # 53 in the electrical section.

If you have opti problems , a $70 pc based oscilloscope is the tool of choice for testing low & high resolution opti signals.
Or these.....

Note that the 93 DTC's have different meanings than the later models, in some instances. The 93 differences are highlighted in the right hand column of the table.
...if this turns out to be your OptiSpark, unless you intend to sell the vehicle soon, stay away from nearly every Opti on the market. Summit Racing carries a reman OEM, same unit GM sells with the same warranty *through GM*, for 1/2 the price. I've replaced 7 Opti's in 12 years. 8 If you count one a member here repaired for me.

When my first Opti went out, they were $550 at autozone -vs- well over $1,000 at the dealer. Dealer is still upwards of $1,000 and is not NEW, dealer Opti's *are* reman now. They will not offer that information unless you ask. "Aftermarket" Opti's, are selling as low as just under $200 now at the local national retailers. Not worth it. Unless, as I said, you plan to sell the vehicle soon.

Point is though, I have spent well over what a new OEM Opti would have cost all those years ago. ...and I'm not even factoring in the cost of the anti-freeze. Most of my Opti's were in the $450 range.

I can truthfully say that with the aftermarket Opti's, I wouldn't trust my car to be driven any farther than I could walk. There is no joy in starting you car everyday and wondering if this is the day she dies.

Yes, I AM trying to scare you. I do not want you to suffer the misery of OptiSpark replacement every 6,000-10,000 miles like I have. Google around, I'm being truthful. There used to be "better than OEM" Opti's out there, no longer the case. Those companies lowered their standards and quality. Even reputable "performance" brands have greatly slipped in quality/reliability.

Your best choices are OEM Opti, or, conversion to LS1 style ignition.

Of course, if you do go the the aftermarket route, you'll soon be able to do Opti replacements in your sleep. You will become very proficient in the procedure and it won't even seem like such a chore.'ll soon enough be as routine as changing your tire. *trust me*.

Just to give you an idea how crap the aftermarket units are, AutoZone will sell you a complete Opti for *less* than they sell the Cap&Rotor. ...It amazes me to no end.
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well it was running fine then it died driving down the road and put a new coil and module on it and it ran for a day and now wont get fire coming out of the coil but it has power going to the coil. and we know the coil and module are good cuz we took them off a running firebird. if the opti is bad will that make the coil not spark or what?
There is also ICM ( ignition control module) to consider.

Both opti and icm need diagnosed. The information to do so is in the factory service manual and at

FSM is pinned at the top of this forum.

Did you pull any codes as per sea dog's instructions? You MUST start there.

Edit: i see you replaced the module as well. STILL TEST IT! Factory Service Manual is your friend. It is over 3,000 pages of highly detailed troubleshooting / diagnostic information. There are flowcharts to walk you through every issue and trouble code you encounter. It's complete with voltage and resistance measurements you should expect to see, what to do if you don't, part locations, removal/replacement proceedures, tools required, potential substitutes for those tools, etc. If you can use a table of contents you'll be an expert as soon as you crack the manual open.

...and yes, the Opti is 2 things. The back half is roughly the equivalent of a modern crank trigger, and the front half is just lIke an old-school distributorS cap and rotor. The rear section is refered to as "the optical portion", when it fails, the computer basically has no way of knowing which piston is where so it won't even try to fire the engine. Optispark ignition system is complicated compared to either old style ignition or modern distributorless ignition. I refer to it as the bastard son of both systems. It's not hard to comprehend or diagnose at all. Just, one-step-at-a-time. Step 1, Codes? I have replaced the ICM when it was the Opti and I have replaced the oPti when it was the ICM. don't start throwing parts at your car. Take a little time, follow the flow-charts in FSM. Get it right the first time.
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ok thank you ill give it a shot tonight, ill be back on tonight with more info.
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