Was running fine and stopped at a gas station the car began misfiring . Found code P306 so did a complete tune up wires plugs coils and ignition control module then reset the code and same code returned. Since then I changed fuel injector 6 only to have same issue sputter and P306 return . Anybody know what else it could be ?

I assume it'* an Oldsmobile? Based on P0306 I also assume it'* a 1996 or newer? What year? Engine? Do you have a compression gauge?

If you click on his profile, you would see he has this info filled out.

Thanks,

Agree with Carfixer, get a compression gage on all cylinders....if within spec, and you have good spark(check with a spark tester), if injector is ok, was the harness to injector 6 ok(can be checked at the external injector harness connector)? Have seen mice eat the insulation under the plenum.....

If that all checks out, I ran into this one time and I chased my tail on it.......turned out to be a vacuum leak......the lower intake gasket had a crack in it, where the port for #6 cylinder was.....a lower intake job was done a few months before.....looked like poor installation was the culprit.....

I would do a running compression test as well. That will pick up things missed in just a static compression test.