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

Weird misfire problem? Anyone faced this problem?

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Old 11-24-2010, 07:04 AM
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Default Weird misfire problem? Anyone faced this problem?

When I first start the car, the engine won't idle well unless I hold the throttle for some time and keep it revved at 1K, but eventually I can take my foot off and it will hold its idle smoothly.

But if I try to rev it up, I can feel it hesitate just before it starts to pick up revs.

If I put it in drive, it will also start to miss and if I put it back into neutral, it won't idle smooth again either and the misfire continues.

My ignition wires are brand new, none are touching any headers, the ignition coil is a new AC Delco unit from the dealership.

Anyone faced this before?
Old 11-24-2010, 08:49 AM
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IT'S THE OPTISPARK!!!

If you had an LS1 you wouldn't be having this problem!

Seriously though has your SES light been on? Did you replace the icm with the coil?
Old 11-24-2010, 09:24 AM
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^^Unfortunely, our new trouble maker could be right, except for the LS1 part. LS1's have problems too (like being slow and looking like a catfish).

My problems weren't quite the same as yours, but my car had some similar issues. I went through every spark plug and wire and thought I fixed it, nope. Monday, I'm sitting in traffic and the car dies unexpectedly and won't crank back up. It was almost like backfiring through the intake when it tried to ignite. Anyway, got it on a trailer and took it home. For some reason, I decided to give it throttle as I cranked it and it fired up, but idled high, had a miss, and just ran like poo. It wouldn't start unless you opened the throttle. Strange I thought. I had the Hi-res and Lo-res Opti SES codes. Luckily I have a brand new spare opti, swapped it out last night and it seems to be running good. The opti I pulled off the car may have been the original one from the factory with 140k miles on it, but I can't be sure.
Old 11-24-2010, 09:51 AM
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Originally Posted by *CAMARO*
IT'S THE OPTISPARK!!!

If you had an LS1 you wouldn't be having this problem!

Seriously though has your SES light been on? Did you replace the icm with the coil?
I never faced this problem before replacing the coil so that is why I ruled out the ICM.

The reason the coil was replaced was due to the terminal getting broken while I was tapping on the timing cover to remove it with a mallet. Learned the hard way by not removing it to avoid damaging it and having to buy a new one for no reason.

I don't get an SES engine when it misfires, which is why I am confused.

The opti-spark did get oil inside it from a water pump drive seal but I did take it apart and clean it up. I don't want to buy another opti-spark, this time I am going EFI 24x or carb if its really the optispark.
Old 11-24-2010, 11:54 AM
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35 visits and 2 posts? Come on some help guys!
Old 11-24-2010, 01:20 PM
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I wish I had some ideas for you but it really sounds like the opti unless there's a plug or plug wire problem, maybe a couple wires got reversed, but I'm sure you already covered all that. It just sounds like a strange set of symptoms for it to be anything but the opti.

Makes you just wanna pour gas all over it and strike a match, huh? I know the feeling, I still have issues with mine that I can't seem figure out.
Old 11-24-2010, 01:34 PM
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Originally Posted by mguidry629
I wish I had some ideas for you but it really sounds like the opti unless there's a plug or plug wire problem, maybe a couple wires got reversed, but I'm sure you already covered all that. It just sounds like a strange set of symptoms for it to be anything but the opti.

Makes you just wanna pour gas all over it and strike a match, huh? I know the feeling, I still have issues with mine that I can't seem figure out.
If the wires were crossed, it would never idle smooth.

I did take apart the opti and cleaned it with contact cleaner until it was sparkling clean all over.

What baffles me is how it will idle smooth, and then start to miss for no reason at all.

And yes, I feel like going down right now and ripping out every wire in the engine bay. I have already built up a carb swap kit in my summit shopping cart.

If I was not busy with my studies, I would have already ordered the parts by now. No point in wasting my money if I cannot touch the car until February.
Old 11-24-2010, 01:42 PM
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I was being sarcastic with the LS1 ****!

It sounds weird, but my car idled fairly smooth when I had 2 wires crossed. You almost couldn't tell it til you reved it and it missed and popped.

It does sound a lot like my car when my opti started going out. The opti had 145,000 miles on it by the way.
Old 11-24-2010, 02:50 PM
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Pull codes before you blame it on the Optispark. However, if you get down to brass tax and its giving you trouble, we offer a value driven alternative.
Old 11-24-2010, 03:08 PM
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You ruled out the ICM without checking it....
Check the ICM before you dump money into an opti, replace it, and still have problems.
Are you sure your misfire isn't a fueling issue? Do you have an injector failing?

You have a lot more work to do before making a decision on what's wrong. Don't sling parts and money around until you really know the whole story.
Old 11-24-2010, 03:17 PM
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Originally Posted by ADM
If the wires were crossed, it would never idle smooth.

I did take apart the opti and cleaned it with contact cleaner until it was sparkling clean all over.

What baffles me is how it will idle smooth, and then start to miss for no reason at all.

And yes, I feel like going down right now and ripping out every wire in the engine bay. I have already built up a carb swap kit in my summit shopping cart.

If I was not busy with my studies, I would have already ordered the parts by now. No point in wasting my money if I cannot touch the car until February.
That is not true if you had a crossed wire it would idle but as soon as you put it in drive and start pressing the gas you will have a pop and buck feel, so i say check your wires and that does not mean go out and see if they are connected. This means take a diagram out there with you and trace the wires with your hand and most of the times is the back two that are crossed ( trust me it happens all the time)
Old 11-24-2010, 03:19 PM
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Originally Posted by qc97z
You ruled out the ICM without checking it....
Check the ICM before you dump money into an opti, replace it, and still have problems.
Are you sure your misfire isn't a fueling issue? Do you have an injector failing?

You have a lot more work to do before making a decision on what's wrong. Don't sling parts and money around until you really know the whole story.
^^^^ this I chased a bad opti for a month before I figure out it was a broken injector wire at the pigtail . My Impala would Idle rough or not at all and then would clear up . Then the issue became it would miss after hitting a bump and would clear up .. I found the broken wire by tugging at the injector wires gently but found one that started to stretch the insulation and indicating the wire was broken inside.
Old 11-24-2010, 04:03 PM
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Originally Posted by chassisbldr
^^^^ this I chased a bad opti for a month before I figure out it was a broken injector wire at the pigtail . My Impala would Idle rough or not at all and then would clear up . Then the issue became it would miss after hitting a bump and would clear up .. I found the broken wire by tugging at the injector wires gently but found one that started to stretch the insulation and indicating the wire was broken inside.
same thing for my MAF leads. the wire appeared to be intact, but upon pulling the insulation back 2 out of the 3 were barely hanging on for life.
Old 11-24-2010, 09:06 PM
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This just goes to show....problems on LT1's AREN'T ALWAYS THE OPTI.
Yes, it's not the greatest design of a distributur. Yes, they often fail if they get soaked and they're not sealed well enough. Yes, they don't always keep stable operation at 7K+ RPM. But, these engines are just as complicated as any other. 1 symptom, 20 different possibilities of disease.
Old 11-24-2010, 11:57 PM
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No, not always the opti, it's a pretty good possibility in this case but I'm no expert. I would definitely rule out the easier stuff first. But like Nick Chandler said, opti's aren't really that expensive anymore, less than $100. A little more if you want a lifetime warranty. And he's good on the warranties.
Old 11-25-2010, 10:41 AM
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And he's been super shady with his business lately. Optis have been showing up dead in the box, people can't get ahold of him, etc.
He lost his sponsorship on LTXTech. Make your own decision about opti buying, but I believe both he and his products should not be trusted.
Old 11-25-2010, 11:04 AM
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I must add that I have taken the car for a few drives and it sometimes drives smooth and great, and the suddenly it starts misfiring and farting out the tail pipes like a pig.

Will have to scan for some codes, but my last opti went out the same way, same symptoms.

Won't know for sure until I scan it.
Old 11-25-2010, 08:49 PM
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Check those injectors and wiring.........
Old 11-30-2010, 06:54 PM
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Originally Posted by qc97z
And he's been super shady with his business lately. Optis have been showing up dead in the box, people can't get ahold of him, etc.
He lost his sponsorship on LTXTech. Make your own decision about opti buying, but I believe both he and his products should not be trusted.
No I haven't, just people who don't know how to install a part mostly or people that can't follow directions. Have some shown up DOA? Sure. A lot? No. Not by a long shot. Its $89.99 shipped. What are you really complaining about? That you're not getting an AC Delco level product for a quarter of the price? Many many many people are very happy with the product.

Here's completely unbiased feedback for the last 180 days from a 3rd party. That's about 30% of our feedback since most people don't even leave feedback. If someone DOESN'T leave feedback, you can assume everything is OK.

http://toolhaus.org/cgi-bin/item-fb?...rk&Check=Check

Here's without our feedback.

With our feedback it usually doesn't even load since there are so many optispark transactions.

http://toolhaus.org/cgi-bin/item-fb?...rk&Check=Check

Like I said, I recommend the first link since the second one rarely loads.
It can take a couple minutes or tries since the tool is often blocked by ebay.

I made 2 posts on LTX tech and both of them say not to use the forums to contact us. I'm not going to log into a forum that has 1\100th of the number of members this place has. I only log into here once every couple days. You have to use eBay\email depending on where you buy.

I don't know the true deal of whats up there since I haven't had time to get over there. But the feedback speaks for itself. You can't please anyone, and we didn't sign up here to grovel to crybabies. I have more integrity than that.

The product and my reputation are substantiated by the numbers and feedback. Just a couple vocal people. Any seller will get that with any product. I could be selling free old fashions from Megan Fox and someone would be screaming "HER THUMBS WERE ALL WEIRD!"
Old 11-30-2010, 07:10 PM
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Originally Posted by ChandlerMotorsports
No I haven't, just people who don't know how to install a part mostly or people that can't follow directions. Have some shown up DOA? Sure. A lot? No. Not by a long shot. Its $89.99 shipped. What are you really complaining about? That you're not getting an AC Delco level product for a quarter of the price? Many many many people are very happy with the product.

Here's completely unbiased feedback for the last 180 days from a 3rd party. That's about 30% of our feedback since most people don't even leave feedback. If someone DOESN'T leave feedback, you can assume everything is OK.

http://toolhaus.org/cgi-bin/item-fb?...rk&Check=Check

Here's without our feedback.

With our feedback it usually doesn't even load since there are so many optispark transactions.

http://toolhaus.org/cgi-bin/item-fb?...rk&Check=Check

Like I said, I recommend the first link since the second one rarely loads.
It can take a couple minutes or tries since the tool is often blocked by ebay.

I made 2 posts on LTX tech and both of them say not to use the forums to contact us. I'm not going to log into a forum that has 1\100th of the number of members this place has. I only log into here once every couple days. You have to use eBay\email depending on where you buy.

I don't know the true deal of whats up there since I haven't had time to get over there. But the feedback speaks for itself. You can't please anyone, and we didn't sign up here to grovel to crybabies. I have more integrity than that.

The product and my reputation are substantiated by the numbers and feedback. Just a couple vocal people. Any seller will get that with any product. I could be selling free old fashions from Megan Fox and someone would be screaming "HER THUMBS WERE ALL WEIRD!"
Being a business man my self and own my own business you are 100% right...cant please everyone but the people that wants to be pleased


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