99 f250

[coxy]

I got a 99 f250 with a 5.4 the motor was shot so I got one from a 01 and put it in the motor ran fine till I put it in the 99 it runs good till 2000rpm then will skip get it up to 3-4500rpm runs great every computer that gets hooked up says the truck does not have a miss fire and shows no codes  ??? the 99 motor had the emission coming out the manifold on driver side the 01 does not have it so there no place to plug the one set of wires in could this be making it skip and not throwing a code im  done working on it and so is the other 3 shops they told me not to come back  ;D any help please and dont say its a ford  :D thanks paul 

[ohiowoodchuck]

It could be leaning it out causing the misfire at that rpm. Can you take the stuff of the 99 motor and put it on the 01 motor. Does this plug go to a o2 sensor. I know if something goes wrong with a o2 sensor or the wiring it will cause the mid range skip/miss. They will run fine at idle and wide open because your actual sending the computer into a default which will over fuel the engine. Another thing to check is to ohm out each injector. They should be around 15 ohms. This could cause the problem also. That's what I hate about most mechanics anymore if the computer dont tell them what's wrong or they can't read it in a book there lost. They forget the basic concept of a engine. It's got to have air, spark and fuel. 

[mike_belben]

Do you have a scan tool that can show you live data while engine is running?

[GRANITEstateMP]

What Mike said.  A scan tool with live data or map data, and maybe someone to drive while you look at the scan tool  :-\

[coxy]

the plug I think went to the egr 
looking at the motor on the top by the throttle right hand side is where it hooked then the pipe went to the manifold that is the erg no I dont know crap about these new motors give me a 1985 back thinking of getting a 52 Studebaker only 5 wires 1 gas line and a shoe lace to run the wipers  

[mills]

I had a 2000 with the 5.4 that kept blowing the plugs out of the heads. I think I had to replace four of them before I got rid of it at 170,000 miles. That was two years ago. It would get a come and go miss for a while before the plug let go. Didn't really tie the miss to a certain rpm range. Guy that worked on it for me told me that I was going to need to replace the head if it happened any more. Other than that it was a great truck. Drove it for fourteen years with very little problems.

[mike_belben]

OBDII

Click link above.

Having a serious misfire with no codes suggests the misfire detection is not working right.  Either a crank or cam sensor would be the first place id look. Youd want to go into the live data with a scantool [my actron has been decent to me] and see that it is reading crank position sensor and the rpm rises and falls as it should.  Also study up on what your primary and secondary oxygen sensor values and trim adjustments should be vs what they are.  Coolant temp value vs actual measured temp.  Throttle position sensor sweep range value.  Stuff like that.

Level 2 discrepancies will be the things to chase down.  Im out of practice on it but im sure someone here is a scantool wizard. Take a phone video of your level 2 screen.  Theres too much data to write down or remember.

[ohiowoodchuck]

Mike sometimes they wont show a misfire thru the computer. It could be on the early side of a misfire in one cylinder and the computer responds by richining up the mixture to compensate for the problem  it could also be a spark plug causing the issue. If he didnt change the plugs or dropped one and put a small crack in the porcelain it could be jumping spark on the manifold or if the previous owner dropped one and put it in anyway. I've bought plugs before and saw the clerk drop them in the box and I make him go get me new ones. That problem bit me one time before. I'm not going against what your saying and a scanner is a nice tool to have to diagnose but like I mentioned earlier start with the basics. In my experience I have seen the problem not show up on a scanner and still have a dead hole. I've repaired the problem and then unplugged a injector and got a cylinder misfire. It has to see the problem so many times in a certain amount of revolutions before it will get a code set criteria.

[repmma]

I had one doing the same thing.  Im pretty sure i changed the coil/plug boot and it fixed it (COP, coil on plug?).  Google and you'll find plenty of discussion about them failing in the way you describe and not detected by scanner. 

[Wedgebanger]

99% of the time I've had a misfire with a mod motor Ford (4.6/5.4) it is a bad coil on plug. You can get the Accel kit with all 8 coils for about $200.

[mike_belben]

If its running so rough that hes been to multiple garages, i presume the misfire is significant and the crank sensor should be picking up the speed fluctuations.  Im betting one can verify a crank sensor with a multimeter pretty easy but ive never had to.  

Get/borrow a mechanics stethoscope and a IR temp gun.  Between listening to the manifolds and temp readings it wont take long to find the dead hole.  Listen to injector bodies too, youll hear a distinct click when they work.  A long screwdriver can work for a stethoscope just put your ear on the handle.

 Move the suspect coil or injector to another hole and see if the misfire follows it.  Pretty sure you can test coil on plug with a meter also. Youtube FTW.

I havent had anything efi in a few years and am out of practice on them detail wise.  Never worked on efi fords.

[starmac]

I used to call it a sex change, when I swapped out a small block for a 500 caddy or 455 olds, now swapping the same motor can be worse with just a year or two difference in model years.
The 5.4 went through some changes during those years I know, can't tell you what they all were but I think cam phasers were one of them. I suspect all of the emmissions will have to be hooked back up the way they were originally to work right with the original computer. I can not tell you if that is even possible.

[kiko]

You probably need the PCM out the 2001.  Did the original engine have egr?
If you were able to actuate the EGR with a vacuum tool, at idle, it will make the engine stumble if EGR is working correctly.  This sort stumble that does not code can often be seen it the live data type scanner.