Ford Repair: 99 Mercury Tracer, spark plug wires, o2 sensors

Question
Recently my check engine light started blinking, staying on and turning off sporatically. I have got it checked at Autozone 3 or 4 times coming up with different codes each time and once passing. I have replaced my spark plugs and wire set, cleaned my O2 sensors and attempted to clean the EGR valve. The problem is still occuring. The most popular codes of talked about misfiring in cylinder 1 and 3 and also and insuffcient flow in the EGR valve.  Basically to explain is the the engine is running poorly with some shaking most often occuring when in the lower gears.  The engine light changes all through this blinking, staying idle turning off.  It is not misfiring as often as it says it is.  What is going on?

Answer
I will not offer advise based on autozone, unless you can tell me the actual codes. Then I may be able to help. Remember, they sell parts, they don't diagnose problems. Checking codes is just the first step, then the diagnostic process begins based on the codes or lack of codes.

Escorts had a lot of problems with spark plug wires and spark plugs. When the CEL is blinking or comes and goes that indicates a failure that can possibly hurt the catalytic converter and increase emissions. A misfire strong enough to cause this should be fixed ASAP