mis-fire mystery

[Qiset]

My wife's 2002 Explorer XLT with a 4.6L started missing when warm especially noticeable at idle. With an OBD2 scanner it showed P0301, P0306, P0316. An online search said those codes indicate mis-fire on cylinders one and six.
New plugs and the codes were still there.
I purchased one new COP and put it on the number six plug. The codes were still there.
I exchanged plugs between cylinder five and six and the codes stayed with cylinder six.
I used a noid light and the signal to the COP's looks good.
I also used the noid light to verify the signal to the injectors. Again it flashed as I expected.
A compression test showed good. I thought it might be a bad injector so I swapped the number five and six injectors and the code stayed with six.
I cleaned and checked the maf/iat. Both read in range from what I can find about them.
I didn't find any vacuum leaks but there was a slight fluctuation. Which made me think that
maybe there is something internal going bad and was about to take it in to a pro. Then
the weather came to my rescue. The temperature dropped from in the 90's to where it hasn't been above 60 for the last few days. What a difference that made. The car has no misfire and it won't throw a code. I even took it to get it's yearly emissions test which it passed.
So is it possible that something about the A/C running can mess up the PCM? Or something else? Any clues?

 

[Qiset]

More on this. This afternoon it warmed up to the 70's. The misfire came back.

 

[lincolnshibuya]

I'd probably recheck the MAF since the IAT is also built into it (or buy a new one). Also I hate to say this but are you sure that when swapping cops they were the correct cylinder # or did you clear the DTC after? At this age the COPs on 4.6 starts to show its age and began to misfire, some of them doesn't even throw a DTC but you could feel that it's misfiring.

 

[Qiset]

Makes sense. The air temp sensitivity seems to point to something that measures the air. I know the IAT part of it is just a resistor but the MAF part has additional stuff.
I verified the firing order in both my Haynes manual and from postings online. Plus one of
the COP's was new. Thanks for the input.

 

[Bobmbx]

I'd recommend a quick inspection of your cabling. I had all sorts of intermittent issues that couldn't be explained.

Then I found this:

http://www.explorerforum.com/forums/showthread.php?t=415084

 

[Qiset]

Wow! I know what I'll be doing next. What a great tip. Thanks!