2005 envoy with 127k miles. Changed the plugs and put in a new coil in cylinder1. Still have the issue, next I took out the throttle body and cleaned that and while I was at it switched coil 1 and 2 even though I put a new coil in 1just to see if the new coil was the problem. Still have the same issue code P0301. Any thoughts as to what to try next? Thanks for any help.
if you change the plug and coil for number one and still have the misfire for #1 you should look at the injector. If you switch #1 injector with the next one closest in the fuel rail, then check to see if the miss follows the injector or stays in #1. If it switches then you have a bad injector. If it stay on #1 then I would look for a mechanical problem with #1