Possible opti problems

[Tyler Wheat]

Hey guys. I'm having some issues with the car that have me confused. Here's how the problem began:

I was driving down the highway, went to downshift and pass someone, car lost all spark and has not had spark at the plug since.

I have replaced the ICM, coil, and opti (did all this in someone's driveway off the highway last Monday). I have spark at the coil wire, but the car will not get spark at the plug. Like I said, I have already replaced the opti with a new Delco unit.

My understanding is that should the optical sensor be bad, the car would not have any fire at the coil as the PCM is not getting the signal from the optical sensor. This should also kill injector pulse, which I also have. Fuel pressure is in check as well.

Do you guys think I got a bunk cap and rotor that is not sending along the spark from the coil? I don't really know where to go from here as that is the only thing I think it could even be.

I'm going to get out in the garage tonight and do some late-night diagnosis and see if I can't figure anything out. I'm going to check my ICM and opti harness per shbox and verify that it checks out. I would think if either were bad, I wouldn't have any fire out of the coil though.

Any help is welcome. I'm pretty much shooting in the dark at this point. Thanks in advance...

[Chris]

Even if your sensor is bad you will likely still get a pulse and spark, but it will not be consistent enough to fire then engine. You said you replaced the cap and rotor, this is not the same as changing the optical sensor.

[Tyler Wheat]

I'm sorry I worded that poorly. I bought a full opti, not just the cap and rotor. I'm just wondering if the cap and rotor on the new opti would be bad for whatever reason and not sending the spark along.

It was my understanding that if the optical sensor was bad, there would be no signal at all sent to the PCM and thus no signal to the coil or injectors. Is this incorrect?

I pulled apart the old opti and looked to be in pretty good shape to me. It had very slight corrosion, but all in all, I would deem it normal.

Before the car went down, it was running just fine. I did a 0-100 pull shortly before and had no miss at high RPM. I would imagine if the old cap and rotor were bad, I would have some sort of symptom before it went out, but I really can't figure out what else it would be.

[firebird_1995]

Yea if you are getting spark at the coil, you should get something at the wires. When you changed the opti as a unit, did you take the cap off to locktite the screws on the rotors? Its possible the button on the cap is missing or stuck in all the way. Or the rotor isnt making contact with the button. Either way its worth a peek. You'll be able to remove the cap without taking the whole opti off.

[Chris]

Just from experience the one time I had an optical sensor go out, I was still able to drive the car, ran like shit but I was able to get it home. Short of having a digital scope its going to be hard to actually see the signal. A multimeter will change with the reading but its not going to be a real time visual, just an average of what the multimeter sees

[Tyler Wheat]

Ok guys, I went and got the multimeter out and according to this: http://shbox.com/1/4th_gen_tech2.html#opti_test, there's nothing going on with power at my ICM or opti harness.

I didn't take off the cap and rotor before installing the new opti. Thank god I have the socket to get the cap off. I'm going to take apart the opti and see what the cap and rotor look like and see if I can't find something wrong there. Everything seems to be pointing me toward a mechanical problem with the cap and rotor. We're about to find out anyway.

I appreciate the help. Keep 'em coming. There's no telling what I have overlooked here, haha.

[Tyler Wheat]

Took apart the new opti. Everything looked fine. Still no spark at the plugs, and I still have spark at the opti. It doesn't sound like it wants to even try and fire. I don't get a hit on any cylinder.

Something tells me to take this thing back and ask for another one. That's really the only thing I can think of unless there is something outside of the opti that can keep it from sending the spark from the coil to the plug.

[firebird_1995]

Take the cap off and check for continuity between the lug on the inside of the cap and its corresponding spark plug wire connector. Check all 8 and the center coil button. Then check that your rotor has continuity between the center tab and the tip on the end. If you find no breaks, the cap and rotor are good. Only other thing i could think is to make sure the rotor tab is bent out far enough to make contact with the coil button and that the rotor is the correct length. Good luck

[96LT1355Z28]

Moe told me he once got a Delco unit from the dealer and the rotor was 180 degrees out, the dealer opti's are re-manufactured in Mexico now so that's also a possibility.

[Tyler Wheat]

Opti appears to be good from what I can tell. I will check what you said later today.

Is there anything else that can keep this car from firing? Cam or crank sensors or something along those lines?

[96LT1355Z28]

If you have spark at the coil it has to be the coil wire, cap, or rotor. Even if the spark was too weak to fire the engine you would still see it at the plug if the coil wire, cap, and rotor were working.

[Tyler Wheat]

Quick update- I've got spark, but the car still will not hit. It is a weak spark, but more that what was there nonetheless. Car still doesn't sound like its trying. The arc is not a nice pretty blue, but more of an amber colored arc. Re-checked fuel pressure and I've got fuel.

Now I'm really confused, but I suppose a little spark is better than no spark at all.

[firebird_1995]

How old are the plugs and wires?

[Tyler Wheat]

I have an OTVC kit that is a few years old, but not many miles. There's a new plug on the wire that I have pulled to check spark at the plug. It's a really weak amber spark. The problem was not progressive, however. The car was running great and then just crapped out all of the sudden.

Spark seems to be consistent and on-cue, but it is really weak. New coil, opti, and ICM, too. Otherwise, I would think the coil was the culprit. I've tried both the old and new coil with the same weak spark as a result.

[96LT1355Z28]

Try another coil. I've personally seen a car that had enough spark to light a timing light but not fire the car. A new coil and it fired right up. He had an orange spark not white/ blue at the plug.

[Tyler Wheat]

I have a new coil and have tried both coils with the same result. I may go ahead and return it and order an MSD one for the price. I just took what O'reilly's had on hand to try to get the car up and on the road when I bought it.

[firebird_1995]

Do you have a bright blue spark at the coil but not at the plug? As someone suggested earlier I would try a new coil wire.

[Tyler Wheat]

I have good spark at the end of the coil wire. I think I have it figured out, though. I went through and slightly (and carefully) bent down the rotor and now its hitting on a couple of cylinders, but still won't start. I think I bought a bad opti. I'll send it back and let you guys know when I get the other one if that fixes it. Really weird situation. When someone said that a friend got one that was 180 degrees off, I started to ponder. I've always had really good luck with the Delco unit on my cars and my friends'. Just my luck as of late, I guess.

BTW, is there a good way to tell if you are making contact on the cap and rotor? I couldn't confirm if I was making a good connection or not.

Thanks for everyone's input. Hopefully I'll get the new opti and that will be the end of this thread.

[Tyler Wheat]

Just an update in case anyone else comes upon this thread with the same problems. I replaced the opti with a new one today and she is running good as new. Problem solved and I'm pretty darn happy that its running again.

Only problem is that the opti connector was broke during shipping. That's my luck going against me again haha. I'm going to get yet another one that hopefully isn't damaged during shipping this time! It was a good enough connection that I could verify that's what my problem was, but no way am I driving without the opti harness being secure. These things are tempermental enough as is!