Chrysler Repair: 98 plymouth neon 2.0l sohc, head gasket leak, valve cover gasket

Question
i have a 98 neon that when i cold start it say after the car has been sitting over night or a few hours so the engine is completly cold the engine will miss fire (i believe)for a few cycles then be completly fine. i have changed plugs and wires 3 different times, changed my valve cover gasket so now i know theres no oil leaking onto the wires,also changed the cam sensor,got my ignition coil tested and it's completly fine,for the past few weeks i've even been putting fuel injector cleaner in the good stuff too such as stp and lucas formulas.around a month ago i had the p300 code turning on my check engine light saying i have a random cylinder miss fire since i fixed the cam sensor last week and reset the battery it hasn't come back on.i'm begining to think i need to change out my ecu unless it could just be the crank sensor which i haven't changed yet.i'm leaning more toward switching out the ecu though because whenever i took the car to get the code read (just incase it was different than the p300)the computer would let the code be read once then they wouldn't be able to get back into the system at all

Answer
Hi Corey,
I can think of a couple of possibilities:
Do you see excessive white smoke out the tail pipe at the time you are starting up from an overnight shutdown? If so, then I would suspect a head gasket leak is letting some coolant into a combustion chamber which then causes the temporary missing.
Another possibility is that your exhaust gas recirculation valve (egr) is sticking slightly ajar so that the mixture is too lean for a good idle when you first start it. So check that out by going to the valve, notice a slot in the valve stem located between the valve body and the roung vacuum actuator. Put the tip of a screwdriver in the slot and move the stem back and forth to see if it closes via internal spring-action to a dead stop. If not, then spray some WD-40 on the stem where it enters the vavle body and exercise the stem some more to free up its action.
Roland