2001 Ford Taurus engine miss

Hello rocky here . My motor will run smooth cant feel it run .And some times at idle in park it will miss check engine lite will flash. give it gas it will run smooth again and not miss for 2or 3 days .Then its the same thing all over again.? check engine lite is allways on lately only flashes when it mississ . I was told it had a bad valve from a dealer ? but I think there trying to bend me over never heard of bad valve causing a miss and then going away and running like new . Any idea on whats wrong ?? would you trust dealer with your car ?? IM disabled
and cant afford bending over any more. Im cooked..
Thanks ROCKY