I need help, 98 5.4 expedition. I keep getting a shuddering in the engine, during high speeds and at a stop light. I read the pcm and got the code p0358, and that is primary and secondary circuit malfunction. So i threw a coil pack at it. Still doing it. Any suggestions PLEASE!!!!

 

Just to verify, where was the cylinder on the engine where you changed the coil pack?

 

It was on the drivers side, last one #8.

 

Okay good, many people replace the wrong side because they assume the cylinder numbering starts on the driver's side. When you replaced the COP, did you happen to replace the spark plug as well? I ask because a bad plug can also throw this code (secondary circuit malfunction.) If you feel the plug is good, how was the 2-wire connector going to the COP? Did it seem loose or damaged in any way?