Ok this problem is very intermediate.
About 3 months ago, I drove to work. I was there 30 minutes, got in car, turned key, crank, crank, crank, no start. This lasted about 10 seconds and then it fired up. It hasn't done this since earlier today when it reappeared. I was in a store parking lot. I started the car, and was idling while looking at my phone. I decided to make a quick phone call so I shut the car off maybe 1-2 mins. After the call ended, I turned key over to start car to leave, crank, crank, crank, no start. I turned key to off, and then back over to crank and it fired up. The engine cranks fast, but it just doesn't start when it does this. It hasn't done this all evening since then though.
I've also gotten a lumpy idle at startup sometimes but not always, it's very random, but it smooths out after 1-2 seconds. On rare occasion it's lasted maybe 5 seconds. I've also had an issue a few times where the car will crank, start, stumble a split second and die - then when I turned key over it always fired up and ran fine - but it's maybe done this twice since owning it.
It's just very random. The car runs like it's brand new and it doesn't stumble or stall. It's just this startup issue. It hasn't seemed to have gotten worse. I've only owned the car since august.
I did the upper and lower intake manifolds. Replaced upper intake plenum, map sensor in November. I cleaned the IAC about 2 months ago and this still happens. I haven't gotten a chance to change plugs and wires, but it runs really good. Even -5 farenheit it fires right up on cold start. Car always has lots of power and is very smooth running.
Should I try changing the fuel pressure regulator? New IAC? I really dread doing plugs in this cold weather right now. Any other ideas?