93 opti spark

[Frank K.]

Bought this car new drove it all over the east. Has low mileage on it and I have serviced all problems myself. Purchased Helms manuals when new. The problem back firing since new in closed loop. Stop vehicle when warm(closed loop) hard to start. (like a dead battery) Last time drove no problems Any suggestions would be appreciated!

[Edward J.]

Re: 93 opti spark

Frank. opti spark dist. has a few problems in the early going,what I have seen is if the car develops a water pump leak or driven in a heavy rain and water/ dampness some how makes its way into the under side of cap. it has no way to escape or dry up. as the early distributors did not have a vented system.and symptoms ranged from long cranking and back firing.
The other problem is since the distributor is a sealed system it can create a vacuum internally and the dist.cap can be drawn onto the rotor and cause other issues such as misfires and poor performance. Not saying this is your problem but you have a little history on opti spark early production corvettes

[Joe L.]

Re: 93 opti spark

Frank. opti spark dist. has a few problems in the early going,what I have seen is if the car develops a water pump leak or driven in a heavy rain and water/ dampness some how makes its way into the under side of cap. it has no way to escape or dry up. as the early distributors did not have a vented system.and symptoms ranged from long cranking and back firing.
The other problem is since the distributor is a sealed system it can create a vacuum internally and the dist.cap can be drawn onto the rotor and cause other issues such as misfires and poor performance. Not saying this is your problem but you have a little history on opti spark early production corvettes

Edward-------


There were THREE basic designs of the Optispark distributor. The FIRST design, used only for early 1992, had no venting, at all. These failed very rapidly and a recall was initiated to replace all of them with the SECOND design.

The SECOND design was the same as the FIRST, except that three 1/4" vent holes were added to the bottom of the distributor's aluminum base. These were used through the 1994 Corvette model year.

The THIRD design incorporated several changes. Vacuum fittings were added to both the aluminum base and the distributor cap. A special vacuum harness connected to the vacuum fittings and a vacuum source fitting on the intake plenum provided vacuum powered ventilation for the distributor. An unrelated change involved a change to the drive system. Instead of the spline drive system used for first and second design, the THIRD design utilized a paddle drive system. SECOND and THIRD design distributors are NOT interchangeable, at least not without changing several other parts.

[Edward J.]

Re: 93 opti spark

Joe, I don't really have the any dates on the changes, But in reality none of the systems were not with out problems as the placement of the Distributor was not the greatest for those people who drove there car in a driving rain storm or just left out doors in the humid climate, maybe by the time the 3rd design came about things were better. As for the recall for the earlier 92 cars it was only good if you took your car to the dealership for the repair. As the years I worked for a Chevy dealership It was only a small percentage that got the recalls performed. At the time I worked at the Chevrolet dealership on the So shore of Mass. we were one of the bigger corvette dealerships,

[Joe L.]

Re: 93 opti spark

Joe, I don't really have the any dates on the changes, But in reality none of the systems were not with out problems as the placement of the Distributor was not the greatest for those people who drove there car in a driving rain storm or just left out doors in the humid climate, maybe by the time the 3rd design came about things were better. As for the recall for the earlier 92 cars it was only good if you took your car to the dealership for the repair. As the years I worked for a Chevy dealership It was only a small percentage that got the recalls performed. At the time I worked at the Chevrolet dealership on the So shore of Mass. we were one of the bigger corvette dealerships,

Edward------


I can almost guarantee you that anyone who didn't bring their car in for the recall would have ended up having it replaced later under warranty or out of warranty. The first design Opti was "born to die". Mine failed at 3,000 miles, just before the recall was initiated.

I agree that all of the Optisparks have problems. For years I've called them the "Achille's Heel" of the LT1 engine. The 95-96 vacuum extracted Optispark was a "band-aid" solution for a fundamental problem. I believe it was a solution that GM figured would be good enough to get them out of the Gen II era. Gen II engines were only used in Corvettes, Camaros, and some B body cars (Impala SS, police cars, Olds, and Buicks). They were never used in trucks, the main destination for most V-8 engines for many years now.

[Edward J.]

Re: 93 opti spark

Oh ya forgot about the police cars, we worked on the state police cars at one time and these cars never stopped, the Distributors did not live long.

[David L.]

Re: 93 opti spark

In 2002 my son bought a 1994 Z28 (LT1 engine w/6-speed M.T.) after his 1st year in college (I paid for most of it). While in his 2nd year the optispark distributor failed while driving on Biscayne Blvd. in Miami. We had a Miami Chevrolet dealership replace the optispark for big $. When he returned home to NH in May 2003 I noticed oil spots on my driveway throughout the summer. The oil was leaking in the area of the optispark distributor. When he graduated in May 2005 I gave him my 2000 Blazer with 40,000 miles and I kept the 1994 Z28 for myself. Later in that year the optispark distributor failed once again. I replaced it myself with an aftermarket optispark made by MSD (cost was about $500) made specifically for 1993-1994 models. The MSD optispark distributor has a vacuum tube system to remove any moisture. I have been driving my 1994 Z28 ever since without any distributor problems and without any oil leaks.

Dave

[Bill H.]

Re: 93 opti spark

Bought this car new drove it all over the east. Has low mileage on it and I have serviced all problems myself. Purchased Helms manuals when new. The problem back firing since new in closed loop. Stop vehicle when warm(closed loop) hard to start. (like a dead battery) Last time drove no problems Any suggestions would be appreciated!

Frank, the first thing to do is check the codes. This can be done on your 93 using a paper clip to jump the diagnostic connector under the dash. The procedure is in the FSM or I can email you a slightly easier one on a pdf. The codes will be displayed on your dash.

Opit's can show symptoms then run fine then show symptoms, etc. My 92 ran to 80k miles before the symptoms started to show up (cutting out in my case).

[Bill H.]

Re: 93 opti spark

I replaced it myself with an aftermarket optispark made by MSD (cost was about $500) made specifically for 1993-1994 models. The MSD optispark distributor has a vacuum tube system to remove any moisture. I have been driving my 1994 Z28 ever since without any distributor problems and without any oil leaks.

Dave

+1 on the MSD (if you are not going to have the car judged). Very high quality unit.
I had the chance to look at my MSD at 15k miles (doing an oil pan/timing cover seals replacement). It still looked brand new inside.

[Terry M.]

Re: 93 opti spark

Oh ya forgot about the police cars, we worked on the state police cars at one time and these cars never stopped, the Distributors did not live long.

Both driver cars in my household have Gen II LT1s -- both former police cars. When I got them with 90K on the clock both had their original distributors. I change the distributors every 100K whether it needs it or not. Up to this time I have used GM units (most recently made in Mexico) with no complaints. Unfortunately the only distributor units now available are made in southeast Asia and reports of their reliability is poor. I am fighting an uphill battle to keep these cars running, but it seems I am among too few to keep the parts supply chain functioning. And then there is the availability of tires, but that is a story we all fight. Like Joe, I should have laid in a supply of parts while I could.

[Joe L.]

Re: 93 opti spark

Both driver cars in my household have Gen II LT1s -- both former police cars. When I got them with 90K on the clock both had their original distributors. I change the distributors every 100K whether it needs it or not. Up to this time I have used GM units (most recently made in Mexico) with no complaints. Unfortunately the only distributor units now available are made in southeast Asia and reports of their reliability is poor. I am fighting an uphill battle to keep these cars running, but it seems I am among too few to keep the parts supply chain functioning. And then there is the availability of tires, but that is a story we all fight. Like Joe, I should have laid in a supply of parts while I could.

Terry------


The 92-94 Optisparks can be modified to include vacuum-extracted ventilation. In fact, I believe a kit is commercially available. Combined with the use of clear RTV to improve cap sealing, the 92-94 units can be made much more water-resistant and sealed. However, I really believe the MSD unit is the best way to deal with the Optispark problem, albeit at the expense of original appearance.

[Terry M.]

Re: 93 opti spark

Terry------


The 92-94 Optisparks can be modified to include vacuum-extracted ventilation. In fact, I believe a kit is commercially available. Combined with the use of clear RTV to improve cap sealing, the 92-94 units can be made much more water-resistant and sealed. However, I really believe the MSD unit is the best way to deal with the Optispark problem, albeit at the expense of original appearance.

Joe
The B & D body LT1s all use the third design of the optical distributor, so the vacuum ventilation is the best one can get. Perhaps because I change them at 100K I have never had a distributor failure on my B-bocies, and both are over 250K and still going. Perhaps had I gone with the MSD unit at the first distributor change a decade ago I too would be singing their praises, but my preference was to keep them all GM dispute my interest in functionality rather than appearance.

I was simply lamenting the lack of available parts, just like the C4 Corvettes. I could go on about instrument panel issues also, but this is a Corvette site. There is enough off topic stuff here now.