2006 F-150 stumbles at start up,and sometimes cranks for a bit like an old carb engine does when its cold before it starts....5.4 engine...

no year told, nor when it last run perfect not told
same answer for 100 years on any otto cycle gas engine made car or motorcycle or scooter.
same., and drives fast too, full power work but idle fails.

well , idle is too rich, as are all carbs this old and never serviced.
when it stalls i bet spark tip is wet with fuel or carbon fouled.

or bad fuel. or caused by bad fuel endless for 100years
ive cleaned like 1000s of carbs in 50+ years. endless. me.
it's only a 150cc engine, and tiny carb. my CB750s old and new.
both had 4 carbs and are tricky and must be synchronized
but your's is a pussyycatt. 1 carb small
causes all.
the float needle is bad causing too high float level.
the jets are bad or wrong or dirty. there may be 2 jets one is idle and bad. but most time not 2, just 1 jet and 1 needle.
the needle can be bad , most are this old and bottom of needle is idle section OF NEEDLE and all worn out and now super rich at idLE SPEED
the air paths inside the body of carb must not be clogged
all tiny air paths. checked and cleaned fully.
that is all I can think off off hand.
my guess is bike is super old.
is bike real honda or this trashy china clones of 80 honda.
no year told nor photo of it so we can ahhhh that BIKE,
THE TANK VIEW IS OMG EASY TO ID.

NOT TOLD , FAILS IDLE HOT AND COLD ENGINE BOTH.
Using throttle grip hold RPM up a tad to get it hot first and see if idle reall fails hot.
first 150cc bike owned ever,?yes
the learn this.
we start with mild choke cold and back it off bit by bit until warm.
the chock has a fast idle features that must not be broken.
back it off slowly for 5 mins. then idle works
some have idle mixture screw on the side or is fast cold idle screw.
the cables are not for idle. ever and are set loose side
a stop screw idle and maybe mixtures idle. tool
depends on year not told if honda mikuni made.

It sounds like carburetor problems. Have you tried a new gas filter?
Check if the choke is operating properly-it may be open too far for a cold engine. The fuel level in the carburetor bowl may be set too low. You might also want to check volume flow from the mechanical fuel pump: disconnect gas line to carb and catch the fuel in a container as you crank the engine-watch fuel flow and volume-it should give a pint or two after half a minute of cranking, maybe less cranking time. Also check the needle valve at the inlet for carb-sometimes a tiny bit of trash or debris will clog up the needle valve. If all else fails, try a rebuild kit for the carb-those simple old carbs should be easy to rebuild.
How long since last tune-up?

I agree it sounds like the magnet for the cam sensor, or a problem in the wiring harness.
I don't think the engine will run with the cam sensor disconnected since it needs that signal to set base timing. It can run without the crank sensor once the engine starts.
There is a slight chance the timing chain is getting loose and affecting cam timing too. You may be loosing plastic teeth on the cam gear.

4.3L V6 CPI - center port fuel injection . you need 62 psi .When cold give it a shot of carb.cleaner or starting fluid ! does it start then ?

415-455 kPa (60-66 psi

Did they balance the new tyres ?. warped rotors can only be felt when the brakes are applied,you may have to have the injectors cleaned and flow tested.

a vehicles crank shaft sensor sends a signal to computer, as to tell what revolution the crank is on. you may not get a check engine light. check injectors for leaking in to cylinders, it can cause an excess amount of fuel in cylinder. this may be causeing the no starts and flooding smell. if it starts good warm then check the injectors for leaking. good-luck!! you may also have a bad coolant tempurature sensor. symtoms of a bad cts are--poor cold idle, stalling, slow idle speed, cold hesitation or stumble, poor fuel milage. ( will also ****** timing). its hard to say with out being there, so check out above. good- luck!!

thats it may be the fuel pump, and the reason why its worse when cold its becouse, when you start the engine cold it needs more fuel to function properly and hold a good idle until it gets its normal operating temp, during these moment the ecu increases the injectors pulse duration to get more fuel to the engine and perhaps a low fuel pressure will give bad fuel atomization and it gives you bad idle and cruise quality, I recomend you to check your fuel pressure for abnormal readings it can be easy by the injectors fuel rail, i hope it help's good luck

The mechanic should check on the fuel pump and the Idle of the fuel pump . if the fuel pump is malfunctioning then you have to repair it.Then also the throttle if the throttle is being worn out or malfunctioning then you have to repair or replace it.The Idle should be adjusted because of the engine is stumbling .the reason why the engine is stumbling or the car over heats is that the fuel pump is not functioning good or there is a problem in the fuel pump.and also it is the reason why the engine light goes off when cold because of the engine problem is in the fuel pump.such fuel or is not entering or going to the engine.

hcmartini - did you mean you replaced the ignition switch behind the ignition key? How much would that cost?

Fuel pump is most likely the cause. Probably just barely making the required pressure to start. Needs to maintain 60-66 psi while cranking to start.