So I have a 2004 C70 2.3. The check engine light gives me 3 codes.
intermittent Misfire in Cylinder 1
Cylinder 1 Fuel Injector issue
and Serial communication link (main computer has failed to communicate with one of its systems more than once)

I have replaced the spark plugs and the ignition coils.

it can only be one of three problems at this point, the fuel injector is bad, the fuel injector wiring is bad, or the computer is going out.

but the one symptom that doesnt fit. Everything works perfectly when the engine is cold. No misfire, no rough idling, no problems at all. then the engine warms up and all the problem starts.
My current theory is that its just the fuel injector going out, causing the plug not to work and the computer not to communicate. or the wiring. to my understanding, if the computer were the problem, it would be the entire injection system, not just cylinder 1. Please correct me if I'm wrong there.

But why does it work perfect when cold? thats the one thing I can't seem to reason out. no problems when its cold. warms up and problems start.

any help would be appreciated, I'm replacing the fuel injector tomorrow, But I am still confused.

 

cold engines run better with a rich mixture and the cold metal cools the spark - warm engines tend to misfire with too much fuel. The fuel injector is a solenoid switch - there's constant pressure in the fuel rail and when the ECU signals the injector to open, you get a squirt of fuel. If your injector was stuck in an open position or intermittantly stays open, you get too much fuel... If the solenoid within the injector shorts or opens, the ECU will sense it and throw a DTC. So chain the injector and see what happens...