Hello! We bought this car cheap and don't mind putting more money in it. 291,000 miles. We got it with misfire codes on both sides of the engine, as well as bad cats. The catalytic converters have been replaced (all three) and the COPS are new, as well as Ford spec'd Motorcraft plugs. I replaced bad hoses going to the EGR and PCV. It runs much better, but still rough. I took it down the road today, and after about 8 miles, the engine light started flashing. I'm getting codes P0316, 0304 & 0306. I know what the codes are, so would like to get ideas on where to start looking. I'm going to make sure the COP wires aren't crossed, and I'll check compression on the front cylinders, although I don't think a head gasket is the issue. THANKS FOR YOUR INPUT!

 

That would of been my first question with near 300k, compression.
Flashing CEL is in an indication that enough fuel is being dropped into to cats to cause damage..

 

That would be my guess too. Luckily, I did not have to worry about that one. Even though the wiring looked perfectly laid out, the 4 and 6 cop wires were crossed when we got the car.

She runs beautifully.

 

Glad it was a simple fix!