1999 4.0 E sohc Spark plug socket issue

[Maclain]

Hello, I am having serious issues with my ford explorer, I have had 3 different mechanics look at this thing, and what im being told is that cylinder 1, 2 ,3 are misfiring, when i first started changing my plugs i had trouble removing the middle plug on the passenger side of the car i went under the passenger wheel to get to it, and it ended up being stripped, i used a fix a thred on it, now my car is not running the same, i thought it was because i used iridium xp autolites on it, i did buy some motorcraft, but i dont think it should be making it run this bad, im hoping that i didnt screw into the piston when re threading idk if thats even possible, but if anyone has any ideas please help, i did check the wiring diagram, and they are new wires maybe it is the coil pack but its already been replaced before, i did change the intake manifold and put new gaskets on it as well, im stuck at my place, and my family is out of town so any help would be appreciated, Thank you!

 

[J_C]

The first thing I would do is hook up a scan tool capable of live data and look at long term fuel trims, if it is running too lean, due to a vac leak and if so, hunt for the leak.

I could interpret your post two different ways. Are you stating that the first thing that happened was it was running badly so you had someone look at it and then you got the diagnosis that it was misfiring, -OR- are you stating that it was running fine then you swapped the spark plugs, THEN it started misfiring?

Are you stating that it was running badly before the spark plug change and now is running worse after it? Is there any chance that you mixed up the wires and put them on the wrong cylinders?

Were these professional mechanics and did they charge you? They should have done enough to narrow down the list of suspects, for example checked that each coil was firing. It's doubtful that the autolite plugs are the problem unless they are gapped wrong, which I would have thought you would have noticed when installing them.

Since these cylinders are all on the same bank, I would wonder about a bad intake manifold gasket yet you stated you replaced that. Did you have the fuel injector rail off and reused the old o-rings so now they may be leaking?

I would move away from the ignition system for now and do a compression or leak down test. I would also check the coolant and oil to make sure they aren't mixing together. If you are stranded and can't do these things, we might need to know what you can do for the time being to limit the possibilities.

 

[rasouth]

I've got the '96 4.0 so I'm not sure if the coil pack is the same as the '99 but on mine the coil pack leads are not the same as the cylinder arrangement, meaning on the coil pack you have 1,2,3 down one side and 4,5,6 down the other side. These may not indicate cylinder number. Maybe the wires are mixed up? Make sure the wires are clipped into the harnesses and not just laying across the valve covers. I had a wire that was shorting out because it was not in the harness and causing a cylinder misfire.
As J_C asked, was the engine missing before you changed plugs?