93_LA_Vette

Is there a way to test the Optispark distributor on a 93 LT1 with 92,000 miles on it? I have been having a miss at idle speeds and a backfire while shifting from first to second at WOT. I have sprayed the plug wires and engine with water while under a load and at idle speeds and could not get it to miss. I also changed the plugs. It does not do it all the time (when I try to make it miss it will not) it seems more prevalent when it is cold, but could occur at any time. I am not getting any error codes. I don’t want to just start changing parts out. Should the Opti go out, will it leave me stranded? I am scheduled to go on a 6 hour trip (one way) this weekend. How long does it take to change the Opti and should I replace the water pump at the same time? What else could be causing this? Injectors, ECM, coil? I just would like a direction to go in.

94white-lightning

Look on this site. shbox.com[URL=http://shbox.com/1/4th_gen_tech1.html]

jabez

Pray that it isn't the Optispark.

MPforUSMC

You sprayed the engine with water? Im not Vett guru but thats a bad thing right?

93_LA_Vette

Thanks, I checked that website and still could not find anything that would help me. I squirted water on it while it was cold. I was told to spray the plug wires and vacuum system with a water bottle and a little soap and if it had bad plug wires or a vaccum leak that it would detect it. Nobody has said whether these are Optispark symptoms or not. I'm sure some one else has had this problem before and changed it. Apparently not!

93_LA_Vette

I have also noticed that it is getting harder to start. I use to turn the key and it would fire right up. Now sometimes while you are trying to crank it....it will start dieseling. If you let off the switch it will sit there dieseling, start chugging and finally start running. Sort of like it was flooded or starving for fuel. It has also never done that before.

Pony_Express_Driver

Howdy

Sounds like we are on the same road. I have changed many optisparks. 5 to be exact. See my entry on Delteq here on the web. If your optispark lasted 92K you are damn lucky. All symptoms say it is gone. To replace you have to remove the water pump. It is a pain. I suggest that you go to the web and enter www.optispark.com. This will take you to Delteq's site. After loosing several Opticraps I went this way. I think I got something in the compute wet after the install..but it is running great this afternoon.

redcorvettedave

[QUOTE=MPforUSMC]You sprayed the engine with water?


get the ignition sys scan by good mechanic... should be able to tell you if opti is going bad. again never spray out or near the opti if it gets wet you're on borrowed time ...esp on a pre 95 vette

peace!!!!!!

93_LA_Vette

Thanks!

LTWON

I hope this might help!

I spoke with Gordon Killabrew at the last forum CruiseIn. I have a '92 with the same problems. Gordon is the man when it comes to C-4 vettes. He told me of a GM bulletin(he may have even wrote it when he was in the Corvette Action Center) on early LT-1s that stated the the PROM shuts the fuel at 5750 rpm. This is right before the shift. This will cause a backfire going from 1st to 2nd under WOT. All new PROMs that you can buy from a dealership for 50 'ish dollars have this fuel cut removed to correct this problem.

Now, I did this and while it has improved greatly, I still sometimes experience the backfire. All cases are different. Intake or Exhaust manifold leaks can cause the backfire, too. I'm pretty sure that I also have one or both. If you have never changed out the PROM, I would do so just for the fact that GM has identified and corrected a problem that is directly related to yours.

I had a friend change my Optispark out about 2 months ago. My old one was hedious. I have pictures if you would like to see. The job was about a 3 hour job but took a lot longer because of the Crank pulley being a b*%@h. We had to use some strategic prying while turning the motor with the starter. By the time we came to that decision, it took about 30 secs once the bolts were removed. I would highly recommend changing the water pump at this moment. This is when I found that my bearing in my pump was about to call it quits. Two reasons:

1. Milage

2. If it starts to leak as it gets older, it can ruin your new opti. I was changing my radiator and thermostat out and spilled some antifreeze down the front of the motor. 2 weeks later I was buying my new opti!

I hope this is helpful. I'll see if I can get the number of that GM bulletin. Good luck!

93_LA_Vette

aww....man hate to hear that! Thanks for the info!

bogus

I am betting on a bad opti. To get 92k miles from a first gen opti is pretty amazing.

CowboyNVette

I agree that if you change your optispark you need to go ahead and change your waterpump. I had 72000 on my opti when my waterpump started leaking slightly so when I changed my waterpump i went ahead and changed my optispark too. I have heard that the opti is normally a 70000 mile change out . Also, like someone else said, do not spray water on your engine in the direction of the optispark. This can cause immediate failure of the opti.

I know this isn't what you were wanting to hear but I would rather be on the safe side than not.

93_LA_Vette

Oh man....looks I have some work to do! Thanks for the replies!

bogus

first off, water on the opti will not normally cause "immediate failure". Coolant will tho...

What happens is 2 things:

1) the Opti gets wet inside, mist forms and the mist speeds up the creation of carbon tracing on the cap and rotor.

2) It get wet from anti-freeze. Inside, the cap/rotor deal with the coolant about the same way, it mists, then speeds up the carbon tracing. However, the coolant can - and does - get into the bearings. These are sealed, and never need serviced. However, coolant will get in and eat the grease. The grease goes, so do the bearings. bye-bye opti. That will lead to codes, because the shaft inside will wobble and give false readings.

missing and funky idle are a result of a bad cap/rotor. Alas, the labour is the same to replace just the cap/rotor, so why do it?

93_LA_Vette

Well I tore my car down this evening. Once I removed the water pump I could see where ant-freeze has been leaking from around the shaft and out of the weep hole. It left a trail of green coloring and rust from both places on the backside of the water pump. I have not had the opportunity to remove the plate on the Opti to check out its condition. Now I need to work on getting it back together. I knocked the Harmonic Balancer off without marking it. I see an arrow on it, I hope when I go look at the manual; It will explain how to get everything back together again. I am going to change the Opti, water pump and plug wires while I have it apart (I have new plugs & oil). Can anyone think anything else that I should change while I have it all apart? Once I have it back together, I will post and let everyone know if that fixed my problem or not. Thanks, everyone.

bogus

Sounds like you are making GREAT headway!!! just take your time, it's not a hard job, just lotsa bolts!!!

other things??? hm... serp belt, idler and tensioner pully come to mind.

what wires did you get? plugs?? I recommend Taylor and NGK.

SilverBeast

Late post, but have you checked your IAC (Idle air control) valve? It can also cause the symptoms you've described.

Strick

Here is some light reading for you. I did this project last year and it has been great since. https://www.corvetteforum.com/techti...=231&TopicID=2

Ramrod92

Does this look familiar?