[Paul Michelsen]

My 2003 ZX2 will flash the check engine light and set multiple misfire codes, Po301, P0302, P0303, P0304. Car had 156k miles, runs great, smooth at all rpms, gets 35+ mpg on the highway. This only happens at 2500 rpm and above or about 63 mph! Have replaced coil pack, plugs, wires, timing belt. Help ! Need to pass emissions test ! I am in Aurora IL

 

[Action]

Welcome to the FFO!

Stop throwing parts at the problem hoping to hit the problem. It is very expensive to do that.

Pull the codes and post
Post the mileage
List city and state.

>>>>>>>>>>>>>Action