Help.... I had a problem that I thought was the transmission. The dealer flushed my transmission, but that was not the problem. Here's what happened:

On the first very cold day last Fall, my 93 Vette made a clunking sound as I accelerated beyond about 30 miles per hour. It felt like the car was not getting gas, or as if the transmission could not move to the next gear... I'm not sure. I drove it home staying under 30 miles per hour, only slightly depressing the gas when necessary.

I took it out again the following weekend and let it warm up for 20 minutes before driving. The engine sounded fine this time, but the voltometer was jumping around the middle of the guage and the backlight for the speedometer was dimming at a traffic light. Also, when I turned on the headlights and the radio, the engine revved very low and I thought it would stall. I drove it about 3 miles, stopped the car, went into the store and came out. Then I started the car and drove it immediately. Again, when I accelerated over 30 miles per hour or so, it happened again. It felt and sounded like a clunking noise like it either could not get gas or could not change gears. So, I drove home under 30 and it was fine, again only depressing the gas pedal when necessary.

Now, it is still very cold. I only have the problem when it rains or after the car is warmed up. I'm wondering if condensation is accumulating on the Opti-spark and making the engine misfire. Could that be it? It ran fine all last summer.

Help
:flag

 

How many miles on your Opti-Spark? Is it original? Vented? :chevy
Strick

 

Sounds more like your PCM is going out. The PCM controls injectors, spark, and transmission (94 and up). Check around your area for junk yards to see if they have any of your year. Before you spend a bunch see if the car acts differently with a different PCM.

The ususal symptoms for a bad opti are erratic idle and/or missing at high RPMs. Although, these are the only symptoms the rest are too weird to describe.

 

I don't know whether it is original or not. I've had the car since last June. It has 65000 miles.

 

At what point did the car go to the dealer? I am assuming no codes have been set since you don't mention it. If it were my car (I have only had my vette for a year, so this is not based on vette specific knowledge) I would try to elliminate some easy stuff in the electrical system before going to the PCM - battery, alt, etc. I have had computer controlled vehicles do very screwy things when not fed their steady diet of electrons.

 

Hi again,
Mine is a 92 LT-1 and has 50k on it. I've had it just over 3 years and it ran just fine. I started working on an oil leak in the front and one thing lead to another and I removed the Opti-Spark opened it up and :eek: . It was wet, rusty, and dirty! The seal around the cap was cracked and brittle. Thanks to the forum, I have completely changed out the ignition system. I didn't want to be like a Ford (found on road dead). If you drive in the rain or wash your engine with the mileage you say is on it...............beware.
We, at the forum, can easilly walk you through it. Just ask.
Strick :chevy

 

It went to the dealer in November but they did not find any codes. They flushed the transmission, cleaned the fuel intake and changed oil. What a pain in the ...

 

Is it easy to do owrk on the Opti-spark? Can I do this myself? I am not terribly mechanical. I have a degree in Computer-Oriented Mathematics and am the Webmaster for the Department of Justice Antitrust Division. I'm no dummy, but no mechanic either.

 

The first thing you need if you decide to do it yourself, is a GM Service manual. They are not cheap, but they will pay for themselves in no time. I wouldn't buy a generic C-4 manual like Haynes, I'd go to your Chevy dealer and buy one thru the parts department just for your year group. How is your metric tool situation? You'll need some standards, too. Give yourself plenty of time, you don't want to rush it. Just about any question you have can be answered on this forum. Make this a fun project even though there are difficult (knuckle busting) things to do. Can you raise the Vette? Be safe about it. When you are ready go buy a couple cans of Gunk and clean the front of your engine off. It's better to work clean. Don't worry about the Opti-Spark getting wet, you're taking it off anyway. Take some pictures of the engine compartment so you can see how parts go back together. The service manual will also help here.
When you have this done, give the forum a post.
Glad to help as I just did all of this.
Strick

 

Thanks Strick!

 

Oh one more thing, Your problem may not be your Opti-Spark, but I'm willing to bet that if it is the original and not vented, it is about to quit on you. My feeling is that the ECM (the computer) would have given you a code if it were the problem. I know I'll feel more confident driving up to the Corvette Bash this summer with my new vented Opti-Spark.
:auto:
Strick

 

I too just finished R&R of the optispark on my 96. Yes, a non-mechanic can accomplilsh it (although my degree is in Aerospace Engineering, so I'm closer to a mechanic than you are I guess!). Run searches on this forum and correlate all the relavent data you can to get a better idea what is involved. Then pop that hood and eyeball just what you are planning to do. Besides the shop manual (necessary) you will also need tools. Since you said "not very mechanical", I thought I had better mention that. Besides the standard stuff (wrenches, ratchets, sockets, screwdrivers, etc.) I had to use two separate torque wrenches, and buy two more socket adapters I didn't have yet. I also got to use my Christmas GearWrenches, which are awesome, but I digress. I was sent the wrong parts by Summit twice. Due to an error in the shop manual, I spent an entire evening searching for a coolant bleeder screw that does not exist on a '96. Wrangling the waterpump, gaskets carefully coated in RTV, and all six bolts back into place kicked my butt. Of course when I work on other people's cars things always go smooth. Go figure. There is also a good list of things you might want to do while you are in there - water pump, plugs, wires, thermostat, flush coolant, etc. Just a short list of the joys of working on your own vehicle. On the other hand, I know it was done right.

Even given the aches, pains, and frustrations, I'd rather do it myself. BTW - if you do it yourself, and you are trying to get the elliptical knock sensor harness connector off of the knock sensor to drain the coolant from the block - carefully squeeze the major axis of the ellipse and it comes right off. See - that math degree will come in handy! (I know, conic sections probably aren't your specialty, but I couldn't relate binary or hex to the car.)
I would still check the obvious and/or easy stuff first. At least make sure the battery is healthy. I had a '97 Dakota with a dead battery that acted just like my '96 with a bad opti (wouldn't idle, could barely keep it running with throttle).

 

SEE, what did I tell you. More help than you need. This is a great bunch of Vette guys. Lets see major axis of the ellipse............is that English? :confused:
Strick