i have a 2009 grand Cherokee with a 5.7 hemi,if you get above 3k rpm it starts missing.it's always no.3 cylinder misfire,if you turn it off and start it back it runs fine,kick it up to 3k starts missing.i pulled the no.3 injector connector off while it was missing an it wouldn't light my noid light,shut it off start back up and noid light flashing like it should.all wiring looks in good shape.any ideas short of going to stealership.thanks,sam.

It should always have power and get ground supplied by the computer. You need to check the ground signal at the PCM...In my opinion, the symptom sounds like it could be the PCM since is clears up when restarted...