4.0 hard to start when cold

So on my '96, I've noticed the engine doesn't like to start right up when the engine's cold. I'll turn it to run, wait for all the lights and buzzers to go off, AC and radio completely off, turn the key to start, starter cranks just fine, but the engine doesn't fire right away. Sometimes it'll catch on the second try, but even then the engine seems to take a second or so to get up to idle speed. Pressing the gas pedal ever so slightly does seem to help. Once it's started it runs fine, no missing or stumbling, seems to have plenty of power, etc, etc. My Haynes manual has a section on "troubleshooting" this and lists the follow potential causes-

1. Battery discharged or low. (Just replaced it with the best battery I could get from NAPA about 2 weeks ago. Also replaced the battery cables with the shortest 4-gauge cables that would work.)
2. Fuel not reaching the fuel injectors. Check the fuel filter, lines, and fuel pump. (Maybe, but like I said, seems to run fine once started.)
3. Choke inoperative (Not really an issue since I don't have a carb.)
4. Defective spark plugs (Checked them when I bought it and they looked normal, nice brownish-red color, could probably check again if need be.)

Ideas? Right now I'm thinking some sort of IAC issue, but it idles fine once started. Slight tick at idle, but I think that's due to a crack in the header. I do also have a P0420 code (Catalytic convertor efficiency below threshold), but again I think that's probably due to the cracked header. My other thought is that the fuel injectors are worn out/dirty and not doing that great a job of delivering and vaporizing the fuel when cold, but exhaust heat compensates for it when warm. Just wanting to know if anybody else has had this problem or other ideas as to what it could be.

The only two starting issues I've ever had on my 96 was the IAC or the CPS.

Try starting it with around 1/8 th pedal, if it starts better it may be your IAC is sticky. I periodically spray a little oil into the IAC opening while the engine is running, the spray oil does a pretty good job of dislodging the thick gunk that coats everything.

Before the CPS gets way bad it may go a little bad, it can fail incrementally.

I did have one episode where the oil was leaking from the rear of my valve cover onto my CPS, it acted just like a bad CPS. Cleaned the oil off and all was good again. I don't have a clue why being oil soaked affected the CPS, but it did.

Sounds good, thanks. I was already kinda thinking of finally getting the engine bay degreased and pulling the throttle body for a good cleaning as cheap weekend projects. I'll be sure to check the CPS and pay extra attention to the IAC opening. What sort of oil are you using? Penetrating oil? Regular engine oil? My thought was squirting some cheap ATF from a spray bottle I have in there. I know some guys will give a warm, running engine a squirt or two of ATF into the intake tract to help improve the idle quality and vacuum...

I just use some Henkel (different brand names, same stuff called Caramba here) rust loosening and lubricating spray. The oil gets under the grime and you don't have to worry much about washing away the lubricant (grease) in the piston worm gear inside the IAC like a solvent might do. A few small squirts is enough. Word to the wise, super glue the nozzle extension on there or make sure it is on there really good. I came really close to losing one down the TB.

I'm not a fan of spraying anything down the TB and through the intake manifold. That crap has to go somewhere and through the intake valves, into the piston, out the exhaust valve and through the CAT seems like a poor choice IMO.

Be careful washing the engine bay, especially around the TB. Some sensors aren't very water resistant. Neither is the distributor.

I usually spray my engine bay out often, really hot water at the quarter wash. It may be better to wash it off a little at a time, than trying to get it really clean all at once. A lite spraying, with really hot water that evaporates fast, seems to work out better than soaking everything for extended periods. Don't get anal about it, just wash off the majority of the crap and don't try detailing the motor. Oil is a preservative and in the end likely better than rust. I always feel lucky when I come out of a motor wash and the engine starts.

It's not a bad idea to wash out the radiator occasionally, bugs, dust, pollen and whatever gets caught in there. Just be careful not to get to close with too much pressure and flatten the fins.

My understanding is that ATF is safe for the cat and such. Might smoke for a little while, but that's it. I'm also getting this info from an engine service textbook I have and it's fairly new (copyright 2005)

Radiator looks pretty new (paint is glossy, none of the fins look bent, no bugs or stuff in it, etc) so at least something is in the shape I'd like it to be in lol. Any more, I cover sensitive stuff like alternators up with plastic grocery bags and duct tape them closed as best I can. Plan is to spray the engine bay down with some degraser stuff, scrub the really built up stuff with a plastic bristle brush, and hopefully I can find a car wash with hot water coming out of the pressure washer to rinse it all down.

Bad temperature sensor would not tell the PCM to richen the mixture for start. Like no choke on a carbureted motor.