Ive been trying to chase down an issue with my 85 Daytona turbo. When you first start it cold, it runs smooth, no issues, but after about 3 minutes or so and it warms up a bit, it starts to miss and the #4 cyl goes dead. I know this because Ive pulled the plug wire to that cyl and it doesnt run any different. I pulled the others and they all start to run rough. there is spark to the plug too.
I have replaced cap, rotor, wires, plugs, and not sure what else to look at. maybe an injector or would the fuel pressure regulator cause this? It had been sitting for about 4 years before I got it. Just recently replaced the fuel pump too. The vaccum valve or port or whatever you want to call it on the intake manifold was cracked on the nipple headed to the regulator, but I sealed it up pretty well. wondering if that might have something to do with it too. its also a brand new engine, so I doubt its a compression issue.
Any input y'all have would be appreciated.
Thanks!