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

Potential opti issue/question?

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Old Sep 15, 2009 | 06:07 PM
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Default Potential opti issue/question?

Alright, I know everyone loves these "is it my opti?" questions, but I have some strange symptoms/issues that I wanted to run by everyone here before condemning the opti.

A few months ago I swore the car had a slight miss, but it was so slight and intermittent I could never really be certain it was. After ohming out wires and rerouting a few questionable wires and replacing one that ohmed out bad, it didn't seem to be any better or worse. It also shut off while driving once around that same time. I had had an issue with the fuel pump where it bled back pressure as soon as the car was shut off, so I eventually replaced the pump with a new Walbro pump.

Today it shut off on me again and I noticed the car smelt ridiculously rich as/when it happened and as I tried to get it started again. I noticed this the time it happened a few months ago too. It wouldn't restart right away, just cranked. After a minute or so maybe it fired right back up and I drove it another 10 miles home...scared and babying it of course as now I am leaning heavily toward the opti and just wanted it to make it home.

My question with these symptoms is this: Usually you hear of the car missing badly or running terribly or just quitting ad never starting back up when it is the opti and this seems to be very rare and any missing I have is so slight I can hardly tell. Also, it seems to be fine again for months after it starts again, though I rarely drive the car and it could be more frequent if I drove it more. At any rate, I will probably do whatever tests are associated with testing the opti to make sure it is bad if I can, but wanted to run this by everyone here for tonight so I have some more direction or potential problem areas to look at while I am tearing into it later this week/weekend.
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Old Sep 16, 2009 | 12:52 PM
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No ideas? Does the shbox website have directions on how to test the various parts of the ignition/opti system?
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Old Sep 16, 2009 | 01:03 PM
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I would think that if it smells ridiculously rich and won't start it's because it's flooded. If it happens again, try putting the accelerator all the way to the floor and then starting it. It puts the engine into a "clear flood" state and will turn the fuel injectors off so it only burns the fuel that's already in the cylinders.

That said - doesn't sound like the optispark to me. Sounds like you have another gremlin somewhere.
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Old Sep 16, 2009 | 01:10 PM
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friend of mine had the same problem w/ car shutting off on the highway while driving. I now am having this same problem in my car sence yesterday. my friend changed the opti and problem went away. he was told that the weak opti sensor would lose track of the cam position and in doing so the car would shut off as a safety feature.
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Old Sep 16, 2009 | 01:41 PM
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could be the opti as stated above, but I had an issue with my old 355 when I had the stock style ignition that was very simillar to this. Mine ended up being the igntion control module (the little black piece mounted to the head above the coil). Those thing are notorious for going bad and creating massive headaches. Autozone, about $85. Not saying thats it but theres a good chance it is.
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Old Sep 16, 2009 | 06:08 PM
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Yea, I recently replaced the coil and was looking at the control module, but when I saw the GM price at $90 or so, I decided to wait. Guess I can't wait anymore...have to start testing things/diagnosing. As far as the rich smell/start I had...that was with the pedal floored. Once it didn't start and the smell was there, I pushed it to the floor with no go. Waited a bit and checked things out under the hood, tried again and it started. I am definitely leaning toward ignition and will probably either wait and just replace the module or try and test the system here this weekend. Coil is good though for sure...already have replaced it with a new GM one and tested it as well. I will check the module and opti next this weekend probably. Anyone have a link to any kind of test procedures for the opti/module? Thanks.
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Old Sep 17, 2009 | 06:04 AM
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Also, just for info., the coil was replaced about 2 months ago/250 miles ago when I did the plug wires/ohmed them out and found a bad one. I also did the mod spacing it away from the head at that time. I am eventually going to do the over the valve cover wire set-up which would eliminate any questionable wires left and route them a little better in my opinion.
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Old Sep 17, 2009 | 07:46 AM
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Seriously with the long tubes I've found it better to route them under the headers and make your own brackets. I burnt two MSD's becuase the plastic junk brackets holding them up broke. Right now I've got custom Ultra 40's and they're routed under the headers, theres more space down there and they are pretty easy to route. I actually run 6,8,5 and 7 through the space in the motor mount to protect them from falling or hitting anything.
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Old Sep 18, 2009 | 06:14 PM
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I wondered about that when I put the poly motor mounts in but was worried about chaffing or pinching there. Guess it's not really a problem then.
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Old Sep 19, 2009 | 05:14 PM
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Is your Service Engine Soon light on? Could be your coolant temp sensor ($20), it will run rich if it's broken. Go to shbox.com to find out how to test it.

Last edited by bore.me; Sep 20, 2009 at 12:42 AM.
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Old Sep 19, 2009 | 08:38 PM
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Originally Posted by quik95lt1
Seriously with the long tubes I've found it better to route them under the headers and make your own brackets. I burnt two MSD's becuase the plastic junk brackets holding them up broke. Right now I've got custom Ultra 40's and they're routed under the headers, theres more space down there and they are pretty easy to route. I actually run 6,8,5 and 7 through the space in the motor mount to protect them from falling or hitting anything.
same here
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Old Sep 20, 2009 | 08:32 AM
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No service engine light, but being a '93 OBD1 it takes a lot to put the light on. It's not so much that it is running rich, which it does tend to run a bit rich normally, but this was definitely worse. Far more unspent fuel as this issue was occurring than normal driving/running. I will check out the temp. sensors again, but I think this is more related to ignition...this weekend got away from me and I will be checking the ICM and other stuff Monday. I would love to find it to be the ICM rather than the opti. I honestly have just parked the car since it happened Thursday and not even fired it up since until I have time to properly test it. I may try and drive it into work Monday to ensure I have some time to test some things...hope it doesn't strand me there :-p

Originally Posted by bore.me
Is your Service Engine Soon light on? Could be your coolant temp sensor ($20), it will run rich if it's broken. Go to shbox.com to find out how to test it.
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