Engine runs rough at start

We need to check a couple things first to find out what this could be.

First, we need to check the fuel pressure when this is running rough and then when it is hard to start.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Once we know what the fuel pressure is when this is happening the next thing is to find out what the o2 sensors are doing.

Basically, we need to find out if the sensors are showing rich or lean.

If they are showing, there are no issues then we may have an o2 sensor issue.

I am attaching a chart below that will help with figuring this out and so let's start with this and go from there.

Thanks

Has this vehicle been sitting for any amount of time or is it a daily driver?

If it has been sitting, then I would completely drain the fuel tank and put fresh clean fuel in it and think about changing the filter as well.

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

With it being a Corvette, they normally sit so I suspect you have a fuel quality issue.

Okay. When was the last time you put fuel in it? If it was more than 60 days, then I would drain the tank completely and fill it with fresh fuel.

Don't try and use additives at this point as they are just chasing the problem. You need to start fresh and then if you want to add a bottle of Seafoam or fuel stabilizer then that is fine.

The reason is, as fuel sits, it absorbs moisture from the air. Some moisture is fine but once you tip past that point, you will not correct it unless you drain it and add all new fuel.

Plus, if you are only going to drive 1000 miles per year, I would only put enough fuel in it that will get you through the drive that you are making. Meaning if you are going on a 20-mile drive. Just put a few gallons in it.

Also, don't store the fuel in the tank. Meaning get a 5-gallon fuel container and fill that and treat the entire 5 gallons with stabilizer and then when you are going to go on a trip with the car, put that fuel in it at that point.

Those fuel containers seal the fuel better and prevent moisture from getting in better than your fuel tank does.

Let me know what happens with fresh fuel and we can go from there.

Thanks

Okay. There are a number of ways to do this. On this vehicle, I would just siphon it from the filler neck. You can buy all sorts of different pumps that will do this easily rather than sucking on a hose.

Another way is to disconnect the fuel line and run a rubber line into a tank and then turn the ignition on and let the pump drain the tank. You will need to cycle the key a bunch of times if the tank is full.

So, I would just get a pump and siphon it.