My Jeep has an intermittent miss at startup that has happened on about 3 of the last 15 starts. It misses for 5-10 seconds and then runs normally. While it’s missing, If I rev it, it misses even worse. It has also been pinging occasionally at 1500-1800 rpm when climbing hills on the highway. It’s A 2004 Rubicon with a 4.0L and 5 speed manual. It has 52,000 miles and I replaced the plugs about 1500 miles ago. I bought a new coil rail that I haven’t installed yet. I’ve ran some BG fuel system cleaner thru it after the last oil change a few weeks ago. I thought tomorrow I would pull the plugs and check them and then swap out the coil rail. The fuel mileage has dropped from 15-16 mpg to 11-12 mpg. Any suggestion on what else to check? I haven’t gotten any codes.
