I am reposting my original reply to most recent post just to address this specific problem...

My 2001 Lightning has problems.... I have 70,000 miles on it, but only 300 on the brand new longblock....

Here are my issues:

It has a very hard time starting, I sometimes need to floor it to get it started

Idles very very rough, the idle flucates between 400 and 700

When driving if I let off the gas it "lopes" and I can feel the truck lunge down almost as if it is switching from drive to overdrive, but not that severe, and it happens in all gears...

I REALLY could use some HELP!!!!!!!!!!!!!!!!!

Thanks,

Bill

 

You could have a tq converter issue? It may not be unlocking all the way and causing all the surging your speaking off.
Other then that I'll place my bets that you have a severe vacume leak of some sort.
Have you tried posting this over @ NLOC ?
One more thing.. You may want to swap MAFs with someone and see if that clears it up. A dirty MAF will cause all the issues you have!! Hope this helps.

 

Check the IAC valve, take a hammer and gently tap it and see if it clears up your problem, if it does then replace it. Don't worry this is a proven technique that has come down from Ford to their dealers service shop.

-Sly

 

IAC was replaced by the dealer when the engine was rebuilt...

New TPS and EGR valve was installed about 4,000 miles ago...

THE CEL never comes on...

Here is more information... When I start it up and it is idling rough, I can remove the vacuum hose from the EGR and it smooths out, I can then run it and it runs smooth for a while, but then I get the CEL to come on... If I replace the hose after I pull it it also runs smooth but just for a little bit and then it returns to its old ways...

Thanks,

 

Kindof sounds like mine when I fried a coil pack at the dyno. It was running really rough, and had no power. But, I never got a check engine light. You might want to check them and make sure they are all plugged in.

But, I would make whoever put the longblock in fix it

 

check your coil packs, I wonder if you still have the origionals in the truck. Take a look and temm me what color the sticker is on top of the coil pack. If it is yellow or green you have the origional coil packs. If they are black on top you have new ones.

 

The coil packs are green on top...

 

I would say you have a bad coil pack, since you have a green sticker on top. They put a new engine in your truck with 70,000 mile coil packs. You have reached the end of the life in your origional coil Packs, and it is time to replace them.

 

You could go through and check your coilpacks just to make sure. Just pull one by one and if your idle smooths out, you've found the culprit.

 

I believe thats a little backwards.When u pull the coilpacks one by one you will notice a difference in idle getting worse when u pull a good one.When u pull a bad one the idle will stay the same meaning that it is not firing.

 

#4 was a suspected bad one when they replaced my engine... Would one bad coil pack cause that? It runs great under WOT...

Thanks for the input....

 

Check your DPFE switch, it has 2 small exhaust lines connected to it from the drivers side manifold/header. It is mounted on the drivers side of the motor. It COULD be sending a false signal at idle and triggering the egr to partially open. As you look at the electrical connector (backprobing) #1 WIRE or the red wire probe w/ postive lead of volt meter, - side of volt meter to a good ground, you should see approx. 0.2v to 1.3v at an idle, anything above that could send a "vacuum" signal and open egr valve. For reference 4.34v = 8.83 of vacuum or max output for this particular sensor..

Also insure the exhaust lines are attached and not damaged!!!

Goodluck!!

Jon

 

Yes 1 pack could cause that.It always seem to run better at higher rpms with a bad coil pack.I have several ford work vans with the 5.4 coil pack setup and the coil packs are a common problem but when one goes we usually drive it with the overdrive off to bring up the rpms wich makes it more drivable till we get it back to the shop to fix it.

 

as another thing to try.... take all your plugs out and check them. i had my back plugs rusting over and over and over. i finally figured out that water was getting in there from having the trim piece below the wiper cowl off. this piece wedges weatherstripping and prevents water from flowing in that direction.