Loose Spark Plugs - No SEL
I have a 2012 Grand Cherokee Overland with the 5.7 HEMI. During a recent spark plug change I noticed that 4 of the 16 plugs were hand tight (at best). Those same 4 plugs had extensive carbon buildup both on the Cylinder and the CoP sides of the plug. Each of the 4 plugs show no evidence that they had ever been properly torqued - the compression washers remain uncompressed.
In the 30k miles since the dealer replaced these plugs, the Jeep was returned to the dealer on 5 separate occasions to investigate the drivibility issues. With 16 new, properly torqued spark plugs and proper compression, the Jeep runs like new. After confronting the Jeep Service department, they seem certain that there's no way for this to happen without there being a misfire code.
With the CoP producing the proper voltage, the spark plug generating spark, and the spark plug being handtight, would a misfire code (P0300-P0308) be expected? I have had no codes in the past 30K but the Jeep has been running horribly - even unsafe at times.
Any information anyone has would be greatly appreciated!