Hesitation and Rough Idle?

[GJudge]

Hi
I recently purchased a 1976 L48 corvette. I’ve put about 600 miles on it so far. On two occasions and again today, it has a rough idle and hesitates when I first accelerate. Each time it has happened the gas tank is down to 1/4 (probably just coincidence?). It’s fine at higher speeds along highways but it’s frustrating as I drive around town. The previous owner let it sit through the pandemic year with very little gas in the tank so I’m not sure if that’s a factor. I’m sure there must be a long list of possible causes including, distributer, spark plugs, accelerator pump, fuel filter etc. so any help in the diagnosis would be appreciated.

 

[74Ken]

I had many problems like this when I picked up my 74 years ago. I replaced Spark plugs, wires, cap rotor and still had problems. I ended up finding out that the carb was never rebuilt. It was not used to todays unleaded fuel. I had the carb rebuilt by a professional company and the problems went away. Also.....ONLY use Sunoco Premium Fuel "V-Power". It is the only company in Canada that guarantees no ethanol in that gas. Ethanol on ANY carb is bad (Cars, lawnmowers, trimmer, snow blowers, etc).

 

[gdh]

Adding to what Ken said, don’t use fuel with ethanol if you still have your rubber fuel lines as it will eventually cause leaks leading to a potential fire.

 

[GJudge]

I had many problems like this when I picked up my 74 years ago. I replaced Spark plugs, wires, cap rotor and still had problems. I ended up finding out that the carb was never rebuilt. It was not used to todays unleaded fuel. I had the carb rebuilt by a professional company and the problems went away. Also.....ONLY use Sunoco Premium Fuel "V-Power". It is the only company in Canada that guarantees no ethanol in that gas. Ethanol on ANY carb is bad (Cars, lawnmowers, trimmer, snow blowers, etc).

Very good to know. Thanks

 

[GJudge]

Adding to what Ken said, don’t use fuel with ethanol if you still have your rubber fuel lines as it will eventually cause leaks leading to a potential fire.

I’ll pay closer attention to the fuel I purchase. Thanks.

 

[Doug's79]

Costco premium is also ethanol free, in Ontario at least.

 

[gdh]

I always go to Shell, but I think Cdn Tire might be ethanol free as well.

 

[Luke 1967]

I would agree the most likely suspect is the carb. If the car has been stored with Ethanol, that old rochester will have paid the price.
Since you are looking at the fuel system, you should also take the time to check the charcoal (vapor) canister. They do have limited life and you will experience fuel pressure issues if it is clogged. If you happen to have a vented fuel cap that fits, it will provide an escape for those gases…. Just don’t tell your provincial emissions control inspector!

 

[Rruuff Day]

Sunoco is now Petro Canada. Avoid all their gas if you are avoiding ethanol as all octane levels have it. Co-op 91, Shell 91, CDN T 91, Chevron 94, Esso 91 in AB but it appears Esso 91 may have ethanol is some eastern provinces. Costco can be hit and miss due to purchasing their gas from more than one supplier and you never know who's gas you are getting there.