Runs good cold,runs bad when it warms up

this 17 years old a good run. nothing new here on failures this old.
all car fail that is what they all do eventually. (entropy etc)
let me guess never fails in others hands
and scans show nothing wrong, but sure too late then, they are gone.
so is and engine problem, so we focus there.
engines (gas, in order fail for 3 ways)

1. engine is bad, or cat melted (no) and egr stuck open (no)
2. bad spark (fuel can not burn lacking spark so why skip #2?)
3. bad fueling. too much or too little

in that order,

not enough evidence stated.
RPM's sink on start sometimes dies then usually it catches itself, idles high a few seconds then lines out.

runs great hot engine, so I guess fails only cold engine.
so bad spark plugs, bad spark coil boots or bad COPS
or bad CKP or CMP
why not just put in new plugs and new boots,
17years old those are NEVER GOOD.

ENGINE IS: 3.0L 2v or 4v (means 6x2 =12valvs or 6x4=24vavle heads.???? it has COPS, coil over plugs(spark)
6 cops ,6 new spark plugs and 6 new boots.
or learn now scan and drive,
or scan in the morning dead cold as the RPM go nuts
and does it misfire going nuts the RPM> misfire is spark first
or flooding 2nd the cold fast idle speed is wrong (IAC)

all I here is almost STALLS at cold start means why below 800 rpm hot and 1500 rpm cold so stalling is what MISFIRE?
can you prevent the too low RPM and stall with fast right foot action?
I say bad spark if not bad spark that is leaking injector or pair

learn to listen and feel for misfire,
and to use the right foot , adding throttle extra air to make it burn clean. Misfire s mostly violent. felt , heard, and see if you view the engine shack.
that is all I have but scanning it failing is how you fix cars

nobody can fix working car delivered a work car...
I have scan tool that logs and then play them back and bingo
GOTCHA. (P0306, and number 6 injectors is bad) see?

https://www.clubfrontier.org/forums/.../frontier-running-terrible-after-warm-up-1611...

Oct 10, 2014 - 10 posts - ‎5 authors
Hi Guys, Ive got a 2000 Frontier SE with the 3.3 in it. I was sitting at a stop ... Engine started sputtering/misfiring really bad. I was able to nurse it ... Misfire between 2-3k rpm only when hot
10 posts
Aug 19, 2011
Sputtering, stalling 3.3
10 posts
Oct 27, 2009
More results from www.clubfrontier.org

rough = misfire, does the CEL glow running, (check engine lamp)
misfire has over 50 causes.
cold only misfire.
i guess you never scanned it or had it scanned, that it?
that be like first after a tuneup, ever get on in last decade?
lets say it was turned up and sparks now good.
and misfires. P03xx codes? we scan to learn that it has codes or not. codes means ERRORS< aka. DTC errors.
to see all errors takes skills, (some take 1,2,3, trips to see them all)
and looking in PENDINGS (and OBD2 term) for early errors.
you have new coils /plugs. good,

examples, the full scan of all live data tells me which path to follow.
what if the scan tool shows you
the ECU reads 150f all the time, (wrong)
and it really is 150f hot, bad thermostat. (or silly fail safe version latched open, omg....)
or it really is 180F and the ECT is bad. (IR gun tells me truth)
see?
just one example of misfire. there are many many more.
but cold misfire (not spark is:)
1: bad fueling. or bad engine, compression tests pass?
bad fueling has many causes. engine bad, stop, NOW.

a: fuel pressure wrong. not spec.
b: ECT reads low for hot.
c: injectors leaking or clogged (see "injector balance testing")
d: clogged fuel filter if engine bogs. (its NOT IN THE TANK)
e: other ECU inputs wrong, did i say scan it>?
f: FPR bad. (see a. above) it too is not in the tank yet.
h: MAP reads wrong, see e.?
I: ; more, ill stop now....

Diagnose Engine Misfire - Auto Diagnosis Repair Help

www.aa1car.com/library/misfire.htm

The engine may shake so badly at idle that it causes vibrations that can be felt in ...The engine may only misfire and run rough when cold but then smooth out as ...

What is causing an intermittent misfire only when engine is ...

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Jun 27, 2013 - NOTE: You MUST restart the engine for the misfire to go away. ... in an expert to do that test, but it might be worth it to prove/disprove the injectors being thecause. 0 ... The first is that the car should run fine even on cold starts.

Engine misfires when cold but runs fine after warming up few ...

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Mar 24, 2009 - They also gave it to me because of this misfire problem it has. ...Engine misfires when cold but runs fine after warming up few minutes later? ... and you start next morning will also cause a misfire until it burns off the coolant.

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www.peachparts.com > ... > Tech Help

Jul 13, 2011 - My moms old 300SEL (with the M103) that was once my car is now my "work car" again as she is getting a brand new SUV very soon.

Cold start misfire solved (finally!) - Bimmerforums

missing a little and running hot are indicators that you could have a head gasket problem. have it tested for a bad head gasket. the missing could be caused by coolant leaking into the cylinder causing a misfire, because of a bad head gasket. running hot is another indication of head gasket. if the rad cooling fan working properly. I think these have what is called a clutch fan which means, when engine is cold the fan turns slower than it does when its warm. if its turning slow when warmed up like when its cold it could be the fan causing the hot running.

Sounds like you have a misfire before the car is heated up properly. Because it runs well after warmed up, I'm thinking that your fuel system, and compression are good. The only other thing that could cause a misfire is an ignition problem. Most likely you have a spark plug that is fouled and does not work well or at all when the engine is cold, but when it warms up to the proper temp it self-cleans and begins to function again.

Another possibility is bad fuel that does not atomize easily when the engine is cold. I would change whatever hasn't been changed in awhile. Spark plugs or fuel.

Just means it isn't warmed up yet when sputters and misfires. Most likely a bad connection on the temperature sending unit in the engine or that sending unit is faulty. This sending unit tells the computer when engine is warm or cold and has to be functional. When working properly, it tells the computer to put engine in cold start mode, which it is not doing. The sensor is stuck in open position or warm mode and not giving the engine enough fuel when cold making it misfire and sputter. Fix that and you'll have no other problems with revving either.

good day, you might want to replace your engine oil with some anti freeze additive, may work just fine. hope this helps, have a nice day

What grade of you do you have ? must be 5/30 fully synth or it breaks down when hot and makes for a misfire.

Could be aging ignition cables letting you know that winter is coming and the condensation that can form overnight can invade cracks that can bleed off some of the high voltage you need at the spark plugs. After the engine is warm, leaky cables can temporarily 'heal,' drying out and losing less than when cold.
If they are sufficiently bad, sometimes you can see some sparkling going on under the hood if you park in a dark area. 
If you have 50k on your plugs, it may be time to replace those too.