Today I was installing a new valve cover gasket on my 2000 F-150 5.4 on the passenger side. I disconnected the wiring harness from the coil on the number four piston so as to have access to a PITA valve cover bolt. To make a long story short I guess the HAZY GA heat must have got to me because I forgot to reconnect it. When I started her up I began to check the A/C because I had unplugged and replugged one of the connections on it, and noticed that the A/C was not cooling. I then began to search for the A/C issue and realized that I had forgatten to plug my #4 coil back up. Plugged her up, cleared the codes, and the A/C worked.... what does my A/C have to do with my #4 coil being unplugged? I figured maybe some sort of "circuit" or something but I'm a locksmith.... the most electrical issues that I fool with are low voltage locks and that's a bit different from the ignition system on my truck so I'm "electrically illiterate" in many respects. Sorry about the long post but it was an issue of interest to me. Any feedback would be appreciated.

 

Dunno. Maybe the misfire monitor saw that engine speed was erratic and prevented the A/C compressor coil from energizing, engaging the compressor and worsening the idle. Reaching, but that's my SWAG.

 

The computers on these trucks are full of sub-routines to keep you from damaging your engine. There are various situations, such as not firing on all 8 cylinders, that will cause the computer to shut down your A/C and Defrost to avoid over-heating the engine.