Hi guys, I just got me a 94 vette about 4 months ago. The weather is finally getting where I can finally drive it. I took it out yesterday and when the engine warmed up it started poping and stalling real bad. I am assuming this is the optispark or cap and rotor help me out here ??? The guy I got the car from said he just replaced the opti in it before I bought it. He said he bought it from NAPA he also said he got the cheapest. The engine is stock and I don' t want to have to keep replacing the opti everytime it gets wet or whatever is happening.

I read I can use a GM replacement and a modified cap ?

Here's the parts list they recommend:

GM Parts needed:


Optispark for 1992-1994 LT1's PN - 10457702

Cap and Rotor kit PN - 10457735 or

1995+ Distr. rebuild kit (Pep Boys or NAPA)

1996 Vacuum Hose Kit PN - 12556174 or

1995 Vacuum Hose Kit PN - 12555323

And how to do it here :http://www.fierolt1.com/lt1_95_up_OptiReplace.htm

Will this set-up work good or should I spend the extra money and buy a MSD or a Dynaspark? I would rather go the cheaper route as long as it will work good.

Thanks,
Steve

 

This isn't the place to try to save a few bucks, IMHO. That would be false economny. I'd strongly encourage you to consider the DynaSpark, or the MSD instead. You'll be far better off in the long run.

Be well,

SJW

 

Thats what I figured. I found the MSD for $515 shipped. Is this a good price or can I get it cheaper, if so where ?

Thanks

 

If it is the Opti, buy quality.

Make sure your not jumping to conclusions and diagnose the problem first. Throwing money and time at a vette can get very expensive and aggravating. What are the the codes (if any)? Although it does sounds like a typical opti failure

 

I went out to pull the codes today and I have a 16 pin plug. I am new to this but I think I need a scanner for the 16 pin. I guess I'm going to buy this scanner AutoXray CodeScout 2500 unless someone tells me different. So I haven't pulled any codes yet. I also started the car cold and the problem didn't go away(sounds like it jumped time and missing a few cylinders). Last week when I had this problem it went away after cooling down, this time it didn't.

 

You can get codes to display, just need to jumper 2 pins, don't remember which, but run a search and I'm sure you'll find it.

 

I have been searching for a while with no luck. I have a 94 service manual and it says jumper pin a to b (a=ground and b=dianostic term.) if you have the 12 pin connector. I have a 16 pin connector and the manual says use a reader for this type.

 

The 94 has the 16 pin, non-OBD2 connector. It is a OBD1 system though. To enter the diagnostic mode jumper pins 4 and 12. Pin 4 is the ground and 12 is the active pin to be grounded. As you look at the connector, pin 1 is top left, 8 is top right, 9 is bottom left, and 16 is bottom right. After you connect 4 and 12, turn key on but don’t start. It will automatically cycle thru modules 1, 4 and 9. Module 1 is the CCM and 4 is the PCM which you would be most interested in at this time. If a 12 appears, that would indicate there are no codes in the CCM.

If the opti cap is defective, there are no codes that will relate to that. If the low voltage, optical side of the opti develops a problem, it can produce a 16 or 36 code. Many times a bad opti will throw no code at all.

What kind of service manual are you using? If it’s a part stores generic, that won’t cut it. You really need the FSM Helms service manual if you are going to be doing any real work on the car. There’s much differences in these model years and lots of problems require the exact service manual. But don’t throw out your current manual, some of the pictures are good.

Check this site for a list of PCM codes which is module 4.
http://www.corvettedoctor.com/1994_96_DTC_Codes.html

 

Where did you find the MSD opti being sold at?

I'm on the verge of buying a Dynaspark.

Billy

 

Here are a few places.

http://store.summitracing.com/partde...5&autoview=sku

http://www.speedunlimited.com/cgi-bi...l?p_catid=4070

http://www.jegs.com/webapp/wcs/store...60803_-1_10679

http://cgi.ebay.com/ebaymotors/MSD-L...spagenameZWD1V

 

The 94 manual i have doesnt say that. The 94 doesnt have a 12 pin connector, and it doesnt have an A or B pin.

Here is the info you need:

On a 94/95 you can check the codes with a paper clip as follows:

You short pin "12" to pin "4" and turn the ignition switch to "On" without starting the engine.

The speedometer will display any codes using the same protocol as the 1990-1993 model but there are some changes in the designation for the modules plus additional modules are added:

Module "1" is still the CCM module.

Module "4" is now called the PCM module (Powertrain Control Module) because automatic transmission computer control was added to Engine Control Module in 1994.

Module 7 (on the 1996 model only) is the RTD module. (This is the Real Time Dampening module which replaced the Selective Ride Control module in 1996).

Module 9 is the ABS/ASR module number from 1994 through 1996.
Finally, Module "A", the DERM (Dynamic Energy Control Module --- (the air bag control module) will be requested to show any codes.

Just like the 1990-1993 display, you read the codes on the speedometer (big) and read the module number on the trip odometer (small).

A series of dashed lines for instance “ - - -“ indicates no more stored codes for that module.

A code showing as “C12” for the CCM module (module #1) means no codes are stored. So C12 is a good thing to see.

Again, you can cause the codes to repeat by turning the ignition off for five seconds and then back on.

Turn the ignition off and remove the short to restore normal operation.

To clear the codes,

1. With ignition "off" ground terminal #12 of the DLC (use bent paper clip to connect pin 4 to pin 12)

2. Turn ignition "on".

3. Press trip/odo button on the DIC until 1.7 appears in the trip
monitor area of the instrument cluster.

4. Press eng/met button on the DIC & hold until "---" appears in the
speedometer area of the cluster, this will clear CCM DTC'S.


To clear PCM/ECM codes do the following:


1. Press the trip reset button on the DIC until the desired system is displayed. In this case it will be 4.0.

2. Press trip/odo button on the DIC until the desired diagnostic mode(4.7) is displayed on the trip monitor area of the cluster.

3. Press & hold the eng/met button on the DIC until "---" is
displayed in the speedometer area of the cluster, this will clear PCM codes.


To clear ABS/ASR codes do the following:

Same as above but you’re looking for “9.7” on the trip odo

And here are the codes

1994-1995: Diagnostic Trouble Codes
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.

Find out for certain what the issue is before you start throwing parts at it and blaming a system that everybody labels as unreliable. I regularly hose my engine, and last week the upper coolant hose came apart, and leaked all the coolant straight over the engine, and down onto the distributor, which is where it sat til the next day cause it was too late in the night to do anything with the car. If the barstard was going to ever fail from getting wet, mine would be dead by now.

Im not saying people should go out and start hosing their distributors (cause i dont), but i am saying dont believe the hype. Check things and diagnose it all properly before you throw away good parts you dont need to replace.

 

Thank you for this info. This could save me a dollar or two. What manual do you have? I have the GM 1994 Corvette Service Manual ST-364-94-1/ST-364-94-2

 

I have the same 2 books. Its not in there on mine. If it is in yours, its irrelivant info anyway cause you dont have a 12 pin connector. Look on pages 8D-4 through to 8D-10 in book 1. Its all in there.

 

Your right, I was looking on the wrong pages. Well I just pulled he codes and I got a C12, which means I have no codes, now what? The car barley runs.

 

Oh where to start !!! "The car barley runs"

How does it idle?
How does it accelerate?
How does it cruise?
Have you checked all connections to Opti and Coil?
Is it blowin' any smoke out the exhaust?
Have you checked your fuel pressure?
and on, and on and on......

You will need to supply much more specific details of how your engine is behaving before folks can give any decent advice..... Kind of like going to the Dr. and saying "It hurts Doc, now what do I do?"

 

HAHAHA!!! Answer Mike's questions ubove, then add in a couple more of these, and i think it would be a good idea to start from the begining :

Compression test
Coolant CO test
Open loop or closed loop related
Check for adequate spark, starting with the coil wire, and check the coil wire is not arcing on the back of the water pump.
Then check spark at the plug end of the leads, all of them, hot and cold to see if they are making sufficient spark.
Is it better or worse at higher RPM?

Answer what you can there (including Mike's ?s) and we can help you from there.

 

This all happened about a week ago when it got warm, the next day it went away and it ran fine for another week. This time it didn't go away. It now idles with a miss. When I give it any throttle it starts popping "sounds like its comming out of the intake". There is no smoke. I have done no checks other than pulling the codes today. Right off I got a C12.

 

Can you get computer connected to this thing and run Data Master? Even if it just sits there plugged into a desktop, i am interested to see what it says.

Certainly check the spark like i said ubove, and check that the coil to distributor lead is not arcing on the back of the water pump. Check every lead and make sure its got good strong spark.

 

I had the same symtoms last summer. (No Codes) After going with an new MSD Opti, It turned out to be the coil. I replaced it with an MSD blaster coil and it runs like new. Im glad I changed the Opti anyway. I found the best deal at Jegs for the Opti but the coil is high there $50. I got one at the local speed shop for around $25. Just a few suggestions from my experiences.

 

Also, their are some really helpful flow charts floating around on the forum
that give detailed step by step diagnostic procedures. Sorry I dont have access to them. Good Luck!