Hello! Long time reader of the boards, first time poster. I have a 2002 Mustang GT with only mod being K&N air filter. The backstory on the problem is that I parked it in November of last year and didn't drive it again until March. I STUPIDLY chanced it and drove it on the old gas.
It misfires. Badly. I cannot siphon out the gas so I add octane booster and fill it the rest of the way (about a half a tank) with high octane gas. I drive it on that for a bit and it continues to misfire and throws the code for valve 6 misfire. It's due for a spark plug change anyway, so I get Motorcraft nickel plugs and change all 8. The old ones were gunked up, so I did use deep creep to loosen them (I have never had to use this in there before). I did the cautionary air compressor blow out before I removed the old ones. I also know that I rewired the boots correctly. I also used the torque wrench set at 13.5 ft lbs. After the spark plug change, it is now not starting. I expected some nasty smoke and time to burn off any of the deep creep that made its way down there, but I have cranked at 6 times with only 2 times producing a turnover which only lasted a few seconds. It has not thrown a code, but but shows monitors on misfire, fuel system and 'comprehensive components'. Should it have burned off by now? Am I looking at something else going on? All feedback welcome and thanks in advance.