My 85 IROC doesn't start-up right away, like it used to. Now, I have to crank the starter 2 to 3 times for 3 to 5 seconds at a time, before it fires. Sometimes, after firing, it runs really rough and continues up until I stand on the accelerator. After doing so, it usually clears up and runs okay. I'm thinking there's unburnt fuel in the cylinder that's causing this problem. Funny thing is that when it has sat for a couple of days, it fires right up, just like it used to. On one occasion I pulled the number one plug and could smell raw fuel. I replaced the plug, thinking that it was fouled or something, but that has not resolved the problem. Any suggestions would be greatly appreciated.

 

carb? efi?
need more details!

 

1985 IROC-Z, 305 TPI, All Stock

 

You may have an injector or pressure regulator leakage problem. A fuel pressure test would help reveal those.

It's also remotely possible that the cold start injector or control are the cause, but a pressure test might help indicate those as well.