My 1995 LT1 6spd is currently in the shop. It all started when I was on the highway and my car started to buck and sputter when driving in 6th gear below 2,000 rpms. If I down shifted to 5th gear and maintained speed, the problem went away. I decided to get off the highway and see how she behaved driving around town. When coming from a complete stop, the car would buck and sputter in any gear below 1,500 rpms. It would sometimes stall, and I would have to restart it. It would restart, and run seemingly fine until I would start to move again, and then under a load it would buck and sputter and stall untill the car would eventually not start anymore. I towed it to the shop, and they determined that the distributor was bad and replaced the opti-spark ( I had them change the plugs and wires too ). The shop gets the car back together and tells me that it won't start...They checked the timing and said that was fine, the plugs are getting spark, the car has fuel pressure and fuel is going to the injectors, but it still won't start. Does anyone have any advice or provide any direction?????

BTW: The car has 120K on it.

 

I'm sure you've seen the "drill". Any codes? Sounds like they misdiagnosed the problem. Are they still going to charge you? Did they suggest you change the water pump while they were there?

Get back to us with your progress. I hate shops and dealerships.

 

Don't be a hater. I own a shop and try to do good, honest work. The first thing they need to check is injector pulse.

 

What is the injector pulse exactly?

The shop told me that at this point they are kind of stumped because everything "seems" to be working properly and doing what it is supposed to do, the timing seems to be correct, the plugs are getting spark, there is fuel pressure and the injectors are getting fuel. The mechanic said he checked all the sensors (I can't remember the list of all the sensors he checked) that may affect the car's ability to run and they all seem to be working properly. The car doesn't seem to be popping any codes either. He told me that he checked to make sure the control module was working properly and didn't find any problems there, they checked to see if it was possibly related to the shot of switch regarding the ignition key and even that is working properly. I guess they even called in another customer of theirs who has a 95 corvette like mine, asked him to bring his car in so that they could compare what mine is doing in comparison to his. I guess the two cars are "behaving identically" except for the fact that mine won't start. I have not had the opportunity to go to the shop and look at the car with the guy myself, but will be making a trip over there tomorrow and get a detailed list of what has been done and I will update the post when I get the specifics. But any information or help anyone could give would be greatly appreciated.

 

Suggest putting the ECM into diagnoitc mode and see if it responds. I am thinking the your ECM has died. Have the shop remove your ECM and install into other customer's car....bet the car will not start now.

Let us know what you find out.

 

They put the opti on out of time! I did the same thing myself on my 95 so don't tell me they only mount up one way. Have the shop check and if they are getting spark then it is definitely out of time.

I would like to know how they checked the timing. Sounds like BS to me.

 

If it was running when it went in to the shop, I got to assume the whole fuel system is OK as probably with everything else. Assuming they did not break anything and its all hooked up correctly.

My money is on the opti is not correctly aligned on the shaft. Many have done it and if the shop is working to fast and shoved it on its very possible. How many optis have they done?

Ditto on the timing comment.

 

This may be out in left field but is there any chance you have water in your tank? If you get a sample out of the fuel rails you can tell right away if you have really bad gas with water in it.

 

Thanks to all that have posted and given me advice so far!

I just came back from the shop and spoke with the mechanic and the shop owner. I asked if it was possible that they installed the opti incorrectly and the mechanic told me that was doubtful being that it's keyed (he's worked on this car before and I've been impressed with his attention to detail in the past) and he explained how it went together and showed me the old opti so I could see the keyed shaft he was talking about. They say the car has spark, they checked the spark time by checking to see if the number one cylinder plug fires on the compression stroke, and it does and that is why they believe that the car is in time. Maybe there's a more sophisticated method to verify??? They checked to make sure fuel was getting to the injectors, which it is. They checked the ignition control module and that is working fine too. They are going to work on it some more today, but the mechanic seems to be stumped and the computer is not popping any codes.

He tried to start the car while I was there, so I could see what it's doing. The car cranks over, you can hear the fuel pump, but the car just cranks. Once in a while it seems like she wants to start, but all she does is sputter and then die out, and I'm talking a whimpy sputter. This is exactly what the car was doing before I brought it to them, so after changing the opti, plugs and wires the car seems to be behaving the same way it did when I was stuck with it on the side of the road. Read my first post to see what was happening before the car finally "died."

There is one question I have after having been there. Should the air pump turn on while the car is trying to start? The pubs mention how the fuel pump should activate for 2 seconds while the ignition key is cycled on but I, nor the mechanic, can find anything that mentions whether or not the air pump should be turning on as well.

Any new suggestions will be greatly appreciated. I don't know where everyone is, but I'm in central CT if anyone is close by.

 

If memory serves...the air pump runs for several minutes on initial start up.

I don't recall where I heard this, but try to start her with the MAF disconnected. I know it sounds dumb, but what can you lose?

 

My 94 has the same reaction at times when the key is turned repeatedly and the air pump comes on for 2 seconds. I would say that is OK.

I can go out on a limp and say it might not have any injector pulses. That should be easy to check especially for a mechanic. You could try starting fluid and that would tell you if there was no fuel delivered by the injectors. However that’s really reaching and I don’t believe you have any injector problem.

You only have to be off a tooth or two for it not to start. I have no idea how they are checking the timing and if their method is valid. Their words sound good and logical but I don’t know how their pulling it off.

Everybody says they have aligned it correctly, nobody ever believes they messed it up. Only way is to pull the opti and do it again. If the shaft is in wrong, it might be hard to pull out of the opti. You should start the engine before the water pump is installed just to make sure all is OK. Run the engine for 10 seconds before bolting up all the accessories. Its best to at least connect the ECT (temperature sensor in water pump) for a better run up. If you don’t it will run but get rich real quick and stumble.

Other than that, before they wear you starter out, they should pull the opti, that’s my stand.

 

I said it B4, I will say it again. The opti was installed out of time. Everything you say is consistent with what I am saying, nothing else makes sense.

 

My 92 had spark and fuel and wouldn't start(Initially it would restart and idle very very rough). The spark coming off the plugs was red, meaning it was weak. I changed the coil and it fired right up. Very cheap to try(20$ for coil), maybe give it a shot?

It looked like original coil at 138k