Take it to a Ford dealer and have a good tech ride along with you with their fancy gizmo plugged into the OBD2.

 

Hi glc, been there done that. They couldn't see anything going on with their fancy computer during three test drives... They were the ones who convinced me that it was something wrong with the timing chain, then wrong with the engine and after replacing engine with a brand new crate engine exhibiting the exact same symptoms, and yet another test drive with the computer, they told me they didn't know what was doing it and couldn't help me....

 

Like I said, I'd make absolutely sure you have 0 EGR valve operation during the test cycle. That's why I'd by-pass, -it's the full proof way. Who knows, your EVR could be malfunctioning, charging the green line without a pcm command. Also and like I said before, -they will run just like that if that valve is opened or opening when it should be closed.

Just a reminder.

 

Hi again jbrew, how do i bypass the egr? just take the vacuum line off it?

 

Take the vacuum line off it and cap the line.

 

I tried that already i plugged the vacuum line and capped the vacuum port on egr valve, ran no differently.

 

I have been having the same problem on my 99 4.2and I just figured it out I hope this helps you. My truck would hit about 3k and hesitate and not want to accelerate and idle rough also when I would accelerate it would sound like I was missing. My truck was throwing a ton of codes for my o2s and mad sensor. Had them all replaced still same thing. So my mechanic said if it still was doing it he thought my cats were plugged. So what to do without tearing your exhaust apart is just pull out your o2 sensors before the cats and just let them hang drive your truck (it's gonna be crazy loud) and see if it doesn't hesitate at 2 to 3k rpm if it doesn't it's most likely your cats are plugged at least it was on mine hope that helps out bud

 

Or if you're really feeling adventurous you can get a pressure gauge and measure pressure before and after the pressure should be the same if not youll have a high pressure before and alot less after it or even put a vacuum gauge on your intake and see if your vacuum doesn't hold steady at 2500 rpm revving it up if it's clogged it will drop. That's the only thing I could see since everything else you did is brand new. You could also try cleaning it out just by running about 5 to 1 fuel to pure lacquer thinner in your gas tank and let it idle for about half an hour at 2500 rpm or just drive it around for a bit

 

Also on my last comment if you try the lacquer thinner DON'T let it sit in your tank. Add a gallon to a quarter tank or so and run 150 miles or idle at 2500 for half hour then fill it up. It is pure acetone and will eat plastic in your fuel pump.

 

Good, then it's not the EVR. So are you absolutely convinced that the EGR valve is closed? By-passing is easier if you do not know how to bench check that valve. You could blow the diaphragm relatively easy. You need to regulate air into the valve, -not much! In order to determine closer.

The 4six uses a smaller valve compared to the 5four. There is two ways to by-pass. One, just remove it and plug the pipe and plate the plenum. The plate doesn't need to be fancy. Scrap piece of sheet metal or aluminum would do it. You need to drill a couple holes going this route, not to difficult. The other way and this works with the 5.4L valves. I mention the 5four because I'm not exactly sure the 4six valve uses the same size pipe thread connection at the EGR pipe. I think it does. Anyway, you again plug the EGR pipe and leave the EGR valve in place. With a Aluminum or Brass garden hose cap, you plug the valve. It's the same 3/4" pipe thread.
Thing is, there's not much room going this route on the 5.4L's. It can be done tho. The 4six may be easier. For me, its simple and quick to do and removes a questionable EGR valve problem.

Like I said tho, -If you can determine that the EGR valve is closing completely, there is no need to do as described. You can look inside those valves and it may seem to be closed. It may or may not be totally shut and that can make for pro longed trouble shooting lol.

 

That's a strong possibility as well, -which can cause the OP's issue. Not sure if that was suggested yet, -good post for sure.

 

Hi brew, ok, i have it at yet another mechanic... one I trust to figure it out. i had to bring the truck to him, about 45 miles away, where i used to live. I told him whats going on with it, and he also suggested that it could be a number of different things, including the egr valve and the cats. so that was the first things he checked out. he said the egr is functioning properly (closing all the way at idle) and that the cats were not plugged up. He did a pressure test before and after cats. so, he has had it for about 2 days now and is still trying to track it down. I will let yall know when he figures it out.. so far, he has never seen this problem before that wasnt easily diagnosed with fuel, mix, spark or exhaust issues... Thanks for everyone's input! Will keep yall updated

 

Yea, I can't believe it's not something that's been mentioned. I think I would of set fire to it before now. It has to be possessed!

Let us know, I'm curious for sure.

 

Hi guys, latest update. Yes Brew, it must be possessed lol, they have had it in shop for a full 2 weeks now and are still trying to track down whats causing it... if they cant fix it, i might be having a bonfire!!!!!! After i remove and sell the new engine..... LOL Will keep y'all posted..

 

geezz i figured maybe a solid day or tow in the shop would at least figure something out this honestly has me puzzled everythings new i have no clue what could be causing this that has yes to be discovered. Good Luck