Ok so here’s what happened last year car say for almost a year I started it up ran fine I said you know what let’s treat the car I never did in the 7 years I owned the 84 so I filled the tank completely with premium gas now I know I could be a real dumb$$$. I don’t know if the 84 can take premium so I drove with it washed the car and put air in tires by time I was on way home car started misfiring bad and stalled then kept stalling. Keep in mind was like 75-80s out so I finally got it home misfiring. Out in garage. I thought damn maybe some bad gas from sitting for a year or is it the premium gas? So another 5 months go by I moved houses I started car up cranked fine once it warmed fully up still same issue now could be still bad gas from before run it or can’t use that premium gas. So I got it to new house I said I’m gonna find the issue.

so I replaced cap and rotor with msd I replaced ignition wires I replaced all spark plugs. Seemed like it drove fine now it’s 60s out keep in mind seems like it driving fine. So I thought ok prob was a spark plug or wire. So I filled gas again I said maybe I burnt all bad gas out of there was so I put some more premium in it. Then 3 days ago it gets warmer out side it’s 75 out I drive car It’s fully warmed up I drive car to Starbucks I sit in drive thru forever sitting in Drive prob about 20 or more mins next thing I know it starts to miss fire then it stalls I get it back home the whole way home it’s misfiring bad. And it wasn’t on the drive to Starbucks it seems like once it was fully fully warmed up and hot outside.

so I get home and I say these fuel injectors are old so I just sent them to FIC for the hell of it to get rebiult but I checked the spray pattern they looked ok when car is semi warmed up but I didn’t check the injectors when it was stalling so I can’t tell if they were the fault or not.

so I need everyone do we thing it’s bad gas or DONT USE PREMIUM or what can do that on hot days and fully warmed up or do we think injectors once it’s warmed up?

also I did buy some air idle control valves from summit to I’m waiting on them.

sorry this is so long but this is so annoying.

 

The prem gas didn't do anything but waste money on a stock 84, so I wouldn't worry about that as the cause of your problem. I'm not familiar with the 84 but is it throwing any codes? The fuel maps change once the car gets up to running temperature so if it is running fine when cold and then starts running bad at temp it could be sensor related. How's your o2 sensor? Are you sure you don't have a vacuum leak when the car is warm? Sometimes things will be sealed when cold but when the engine warms up it expands just enough to create a leak.

Honestly drawing at straws as I don't know the 84 at all but I do know one thing, the gas being prem isn't your problem.

 

You going to let gas sit for that amount of time use ethanol free and storage additive.

Injectors could be shorting when hot.

Don't throw parts at it! Troubleshoot it.

See South main auto video, no start when hot for ideas

 

Given it seems to be a temperature issue I would probably check coolant temp and oxygen sensors and go from there. But yeah, like @Theman5 said, troubleshooting is better than throwing parts.

 

Yeah, take a look at the temperature when this starts to happen. When my CTS went bad the temp would go up and down by 20 degrees or more. And I got 1 MPG. Ran out of gas. Not a good day

 

Premium fuel will not cause any problems in a 1984 vette. Since the car is having problems you need to check for any stored trouble codes. In the absence of any information other then it runs poorly when hot I would look at your ignition module, when they act up it is ussually at higher temperature.