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My new to me 1996 LT4 quit running and I believe it to be the Optispark. My questions are not "is it the optispark?", they are what part of the Optispark and sources for repair parts. Details:
Car quits running after it warms up, ECM illuminates check engine light and I get PI1371 for a code. The code description is DI ignition low and high circuit is open or shorted. I have checked:
The intermediate harness for resistance and shorts across wires
ECM 5V, 12V reference at the harness intermediate harness
Ignition control module voltage, resistance to ground.
The only failure I see, is pin B on the ICM should have 1-4AC volts when cranking. I dont get that when testing I get 0, that would be consistent with the code, no signal from Opti..
I have ordered a replacement AIP Optispark unit that have good reviews. However I would like to figure out what is wrong with my original GM Opti and fix what needs fixing. Questions:
What would cause the loss of the signal to the ICM from the Optispark? Is it the optical sensor? Everyone says the original optical sensors are the best....
Could something in the cap interrupt the optical sensor signal?
What is a source to buy repair parts?
Thanks.
Petris enterprises is a good source although he may be out of parts at the moment.
Another good source is https://www.ebay.com/str/optidoctor. If your opti is an OEM unit and has the Mitsubishi opto/electric sensor he can rebuild your OEM unit.
Last edited by Mr. Peabody; Aug 12, 2021 at 06:40 PM.
For as often as opti's need rebuilt I have never desired to become an expert at it. To get to the bearing you have to remove the disc without damaging it and mark it so it can be installed in EXACTLY the same spot. Next order a new bearing. This bearing is NOT the same as stock and needs work to fit correctly. The good MSD cap and rotor is almost $200.00. Be sure you see just how much you are getting into trying to rebuild yourself. You might not even save much as opposed to sending to the Optidoctor and getting a professionally rebuilt and tested opti. Dan PS: sending to optidoctor is only an option if your opti is original.
The failure of the low or high-res signal indicates an issue with the optical sensor, yeah. It is possible for that sensor to start failing due to heat. I believe Tom400CID on this forum demonstrated that. In your tests, you should try testing it both cold and hot (after failure). If you get a signal when cold, but not when hot, then you've isolated your problem. At that point, the fix is really as simple as replacing the sensor. I've never had to do that, but I don't know why you couldn't go to a pick-and-pull salvage yard and take the sensor or entire distributor out of any LTx V8 Chevy you find. Then just swap that in.
I just took my LT4 opti apart the other night. Oil got in through the dried out seals. Sprayed it with electrical cleaner, rubbing alcohol and revealed with rtv. I've done 3 optis like this. 2 unvented and this one. If you've never done one before, its not to tricky. I would recommend taking pictures as you take one apart. Easier to put back together with pictures for reference. But really it only goes back together one way. Hope this helps. The GM optis are the best. I bought a Cardone and it grinded at a certain spot when I spun it by hand. Took it back and scoured the land for a GM opti.
I just took my LT4 opti apart the other night. Oil got in through the dried out seals. Sprayed it with electrical cleaner, rubbing alcohol and revealed with rtv. I've done 3 optis like this. 2 unvented and this one. If you've never done one before, its not to tricky. I would recommend taking pictures as you take one apart. Easier to put back together with pictures for reference. But really it only goes back together one way. Hope this helps. The GM optis are the best. I bought a Cardone and it grinded at a certain spot when I spun it by hand. Took it back and scoured the land for a GM opti.
No but I greased them and it helped. Like 50%. It was making a noise because of water exposure. But im curious about your problem. You think the extra bearing friction is heating up the housing causing the issue?
Last edited by 93TALT4A4; Aug 17, 2021 at 08:34 PM.
Hey guys thanks for the info and pictures, My optispark ended up being non original Autozone replacement....
I replaced it with an AIP electronics. I intend to find a used original from somewhere and rebuild it. Once I get it I will come back for more advice.
I wanted to get it running so I didnt replace the oil seals on the front cover, once the weather turns I will get after it all.
Hey guys thanks for the info and pictures, My optispark ended up being non original Autozone replacement....
I replaced it with an AIP electronics.
Yeah, the Autozone ones are terrible. I have friend who got two in a row from them that were bad right out of the box. Same problem: they were missing one of the two signals (I forget which). They aren't worth the labor of installing them. The AIP one should be better.
So for curiosity I took apart the autozone unit. It’s actually well built but they must use junk optical sensors. I am going to replace the optical sensor with the one API uses and put it back together. That way I will have a spare on hand. These are the pics of the autozone unit.
So for curiosity I took apart the autozone unit. It’s actually well built but they must use junk optical sensors. I am going to replace the optical sensor with the one API uses and put it back together. That way I will have a spare on hand. These are the pics of the autozone unit.
Right, it's definitely the sensors on the AZ units that fails quickly or is DOA.
Optispark Experts Step Inside
