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Help! My 1994 C4 Corvette needs HELP!!

BigRich

New member
Joined
Aug 18, 2014
Messages
3
Location
Owenton, KY 40359
Corvette
1994 C4 metallic blackrose coupe
I have a 1994 C4 corvette coup. I got it with 94,xxx mile on it and I have loved every second of it. It is going on 98,xxx miles on it now. I love working on this car and keeping good care of it. Well a couple of weeks ago, out of no where I leave my house and within 100 yards of my house it starting jerking and then it died. After it sat a while it would start for a minute then it would die and not fire at all after that. I took it to my local garage were they said it was the distributor. They put a new distributer on it and a new fuel filter. Well they sent it back to me with it missing. They then said it would need new spark plugs and wire. So I had them put new spark plugs and wire. Well, I drove it home and it was still missing. Then the said it would need new fuel injectors so I had them put new performance 32Ibs an hour fuel infectors on it and guess what. I drove it home and it was still missing!! They said they had no clue after that so I took it to a Chevy dealership and they have had it for two day in the garage and they have no clue. I am trying to get Chevy to tell me what they have looked at but in the mean while does ANYONE have ANY suggestions or idea what it could be or what I should do at this point.
 
Well a couple of weeks ago, out of no where I leave my house and within 100 yards of my house it starting jerking and then it died. After it sat a while it would start for a minute then it would die and not fire at all after that. I took it to my local garage were they said it was the distributor. They put a new distributer on it and a new fuel filter. Well they sent it back to me with it missing. They then said it would need new spark plugs and wire. So I had them put new spark plugs and wire. Well, I drove it home and it was still missing. Then the said it would need new fuel injectors so I had them put new performance 32Ibs an hour fuel infectors on it and guess what. I drove it home and it was still missing!! They said they had no clue after that so I took it to a Chevy dealership and they have had it for two day in the garage and they have no clue. I am trying to get Chevy to tell me what they have looked at but in the mean while does ANYONE have ANY suggestions or idea what it could be or what I should do at this point.

There are a lot of junk rebuilt Optisparks being sold. It's very possible the one installed is junk.
You need to install a fuel pressure gauge and verify the fuel pressure is around 40 psi.
Disconnect the vacuum hose at the fuel pressure regulator and verify there is no gas in the hose.
With the vacuum hose disconnected the pressure should rise to around 45 psi.

The stock injectors were 24 lbs.hr. 32 are to large and you would need to have the engine calibration fuel injector constant changed to use those injectors or you will be running way to rich.

Your original symptoms could have been Optispark, ignition control module, fuel pump or PCM.

Always ask for the old parts back. For the first company that replaced the Optispark, plugs, wires and fuel injectors to say they don't have a clue as to what is worng is rediculous. :mad

Get the car back and troubleshoot the problem your self.
 
There are a lot of junk rebuilt Optisparks being sold. It's very possible the one installed is junk.
You need to install a fuel pressure gauge and verify the fuel pressure is around 40 psi.
Disconnect the vacuum hose at the fuel pressure regulator and verify there is no gas in the hose.
With the vacuum hose disconnected the pressure should rise to around 45 psi.

The stock injectors were 24 lbs.hr. 32 are to large and you would need to have the engine calibration fuel injector constant changed to use those injectors or you will be running way to rich.

Your original symptoms could have been Optispark, ignition control module, fuel pump or PCM.

Always ask for the old parts back. For the first company that replaced the Optispark, plugs, wires and fuel injectors to say they don't have a clue as to what is worng is rediculous. :mad

Get the car back and troubleshoot the problem your self.

I have the old Distributer and the old injectors. The fuel pressure and the vacuum tested good. I agree it is ridiculous that they don't know lol. I have a couple of questions though.


First how would I go about trouble shooting the distributer when I get my car back.

Second when would a corvette need bigger fuel injectors.
 
First how would I go about trouble shooting the distributer when I get my car back.

Here are two videos about the Optispark.

http://www.youtube.com/watch?v=lFCjaz6zHfc

Inside the LT1 Optispark - YouTube


Since the repairs were done, what has changed? You said the original problem was the engine stalled but would restart after sitting.

When the engine wouldn't restart was there spark?

An indication the optical part of the Optispark is working in a no start condition is the tachometer will show rpm as you crank the engine. If you have rpm and no spark could be a problem with the coil, ignition control module, the rotor is loose or Optispark spark distributor cap.

Using a volt meter set to AC while you crank the engine you monitor the drive signal from the PCM to the ignition coil. If the voltage is around 2-4 volts the problem is in the ignition control module, the coil or the distributor cap or rotor. No drive voltage the problem is the Optispark, wiring or the PCM.

When the engine wouldn't restart if you sprayed starting fluid in the throttle body would the engine run?
That could point to a fuel delivery problem.

You mentioned the car misfired when you first got the car back.

A shop would use a scope and verify the high and low resolution pulses from the distributor are stable and the wave forms are accurate. For the misfire they would use scanner software and monitor the O2 sensors to determine which bank of cylinders the misfire is coming from.

If you look at your old optispark, use your hand and spin it, is the movement smooth or is the bearing bad?

You can take it apart and verify there is no carbon tracking in the distributor cap, the rotor is not loose, the optical wheel has no rust on it and there is no moisture or oil inside the housing.

Other than physical verification with out a scope there is nothing more you can do other than replace it.

Most people also replace the water pump when an Optispark is replaced because a leaking water pump dumps water on to the Optispark.

Second when would a corvette need bigger fuel injectors.

Only if major engine modifications are made that requires more fuel such as a Head or camshaft change. Since you now have larger injectors, you've introduced another variable into the problem. I'd reinstall the original injectors with new o'rings. If you believe the original injectors are bad you can send them out for testing but that will cost you close to $100. To have the computer reflashed to compensate for the larger injectors could cost $100.

Have you verified if any trouble codes were set?

Using a paper clip and short pins either 4 or 5 to pin 12 on the diagnostic connector located above
the drivers right knee and turn the ignition On, any trouble codes will be displayed on the speedometer LCD.
Module 1 is for the CCM
Module 4 is for the PCM
 
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I have a 1994 C4 corvette coup. I got it with 94,xxx mile on it and I have loved every second of it. It is going on 98,xxx miles on it now. I love working on this car and keeping good care of it. Well a couple of weeks ago, out of no where I leave my house and within 100 yards of my house it starting jerking and then it died. After it sat a while it would start for a minute then it would die and not fire at all after that. I took it to my local garage were they said it was the distributor. They put a new distributer on it and a new fuel filter. Well they sent it back to me with it missing. They then said it would need new spark plugs and wire. So I had them put new spark plugs and wire. Well, I drove it home and it was still missing. Then the said it would need new fuel injectors so I had them put new performance 32Ibs an hour fuel infectors on it and guess what. I drove it home and it was still missing!! They said they had no clue after that so I took it to a Chevy dealership and they have had it for two day in the garage and they have no clue. I am trying to get Chevy to tell me what they have looked at but in the mean while does ANYONE have ANY suggestions or idea what it could be or what I should do at this point.

Did you get your money back for the Opti, and fuel filter, and spark plugs, and wires, and injectors, and all the other stuff that was good to begin with? And did you get the original parts back that were good?

What tests did they show you that showed that those parts were 'bad'?

I'd START there.

The Fully Automatic Assault Wallet
730_machine_gun_shooting_smiley.gif
repair philosophy (sometimes called Plug N PRay) NEVER, NEVER NEVER works.

Fuel pressure was good? Was that Static FP? Or dynamic? And leakdown time?
 
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Well I finally got the car back and the distributer that was put in that was supposed to be "New" had actually burnt a hole straight through the distributer cap.:mad I called them and they put another new one in for free. The miss is now gone but I was am not able to return the new injectors. I have the old ones. Since I am not able to return the new ones what should I do?? Just keep them and put the old ones back on or what? Also they would not give me the money back for the spark plugs/wire and the labor for the needless work. :mad
 
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Small claims.

Depending on what's on the service order ... ?
 

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