That's a 4 valve engine, and it's not an easy swap.

 

Ive had this problem before it may not be but I would check to make sure the pvc valve hose is connected and secure and take it off to check for any cracks or air leaks they are easily nocked off especially in the process of you putting the motor in it could’ve came loose when the intake or throttle body was going in. Just big possibility.

 

I hope it's fixed, 4 years later.

You really need to look at post dates before replying to a thread.

 

Ok I am confused... I did a engine swap 4.6 to 5.4 on my 1997 f-150 everything runs great.... I am running the 4.6 pcm and the coil pack .... so basically right now my 5.4 engine is still running like 4.6 ... I want to get the 5.4 power so what’s the best option for me i here tuning it and other say swap out the pcm to 5.4 it will probably be cheaper... but if I get a 5.4 pcm how would I know which one to get ? I am thinking probably a 5.4 pcm the same year of my truck (1997) because that year doesn’t have PATS... please help me figure this out .. I think I already lost all my hair trying to figure it out .....

 

You would have to make sure the 5.4 PCM is out of a same year truck with the exact same transmission, like I told you in the master swap thread. You may still have to reprogram it with your VIN, but not too sure about that.

Note - all automatic 4.6 trucks had a 4R70W, but most 5.4 trucks that year had E4OD. The 5.4 never had a manual transmission. If yours is manual, a 5.4 PCM won't work.

I still say you should just get a programmer and custom tunes for your PCM. That will make it run even better than a stock 5.4.

If your 5.4 is out of a 97 or 98, putting a set of PI heads and manifolds on it off a 99 or newer will give you a substantial power boost, properly tuned, of course.

 

So I am gonna call tomorrow about tuning see what they tell me .... so I am gonna get a tuning for a 5.4 since I got motor in and running now right ? evan thou I have a 4.6 pcm

 

Like I said, you need to tell them exactly what you have now so they can advise you properly.

 

It could be because you used everything from the 4.6 to put on the 5.4L

 

This is an old thread but the info is still useful to those who have an issue and need the info..
Cold start utilizes the cylinder head temperature and intake air temperature sensors to tell the computer it's to be a cold start setup at the moment the ignition is turned on before even cranking. The fuel pump also runs at this time for a few seconds then shut off. As cranking begins the fuel pump will turn on again due to the crank sensor detection of crank rotation.
This sets the fuel rich and advances the ignition timing and opens the intake air control for increased idle RPM.
A Carbed engine needs all the same actions for fuel , open throttle/high idle and advanced timing.
Are these sensors hooked up and functioning? These are the only way the PCM has to know it should set up for cold start set-up and control as it warms up to go closed loop for Ox sensors to take over fuel control and bring the idle down to normal after heat builds.
Hot re-starts is the same except for the temperatures sensed and settings calculated.
Is the fuel pressure up to speck?
Is there an intake vacuum leak etc?
.
Once running is the there enough fuel pressure? You need close to 35 PSI at the fuel rails.
These are the basic things you need to know for cold starting, idle and closed loop smooth running.
Which PCM are you using?
The system will not tolerate anything missed.
Good luck.

 

just get a Coputer Tuning and ill Work better

 

question

 

Will this work with a 2010 4.6 Romeo swap to a 5.4?

 

I guess a custom tune is too difficult??

 

You replied to a 2 year old post.

 

Easy swap. Just did 4.6 to 5.4 on my 03 screw. Literally used 5.4 torque converter and had to play with the exhaust a little and everything else was plug and play. Runs perfect on 4.6 tune with no check engine lights. Power is all there as I've had plenty 10th gen 5.4 trucks and know what they feel like.