01 Ford F150 4.2Lv6, Ran good until today, Swapped out the plugs this morning and now it is throwing P0401, P0171, P0174 and it is stumbling horribly under acceleration. I Put the old plugs back in and still the same issue... Any help would be great! than

are the plug wires mixed up?

Swapped out makes it sound like you interchanged them? :-(

Are you trying to say you replaced them instead? :-)

If you replaced them and didn't use Auto lite or Motor-craft that could be the reason for the setting of the codes.

I (Replaced) them lol with auto lite platnium plugs... i did them one at a time to make sure i didnt cross the wires

It ran decent this morning i have checked what i believe to be every vacuum line and im at a loss now.... this is my only mode of transportation as my others are just my hobby cars lol...,

gavin,

You can check every vacuum line and connection till the cows come home, and it's gonna tell you nothin. You gotta post the results of an engine vacuum pressure test. Also look around for something that you could have accidentally broke off or disconnected while changin the plugs. Could also be a freak thing and have nothin to do with the plug swap. By freak thing I mean a sudden second problem. That being a leaking intake manifold gasket. Ford trucks are known for that. Another reason for postin the results of an engine vacuum pressure test, because a leakin gasket is gonna show up in a vacuum test. Keep in touch.

I will have to figure out where to get a vaccume gauge also where should i test the vacuum from? sorry im new at the vacuum testing....

Ive came to realize that this old truck wants to stay just that... Any time i mention Selling it or try fixing something something else breaks haha.... its like a grumpy old man who doesnt want to go to the doctor even though he knows something is wrong... quite annoying

egr and 2 lean codes?
sounds like a vacuum leak to me, and it ran ok befor plug replacement, i'd say you must have knocked a vacuum line or some thing out of place.
you'll have to look at every thing you touched during the replacement.
revese your steps thru the replacement process, even where you leaned your arms on while replacing plugs.
there should be a vacuum routing sticked under the hood or on the fan shroud, use it to check the vacuum line routings.

okay guys i figured it out :D except the egr but the stumble is Gone now and runs good enough

What happened was the new plugs i put into the truck 3 of them had cracks in them causing it to short or spark to the block so i got some new ones in it and tada

Good job Gavin. Glad you figured it out, and that it was somethin easy.

Glad you go it.

Gavin,

I'm postin this for the future plug changes that you're gonna do. The pluga cracked because you were not usin a plug socket. You gotta use a plug socket. The way to tell the difference is with the rubber insert inside a plug socket. A regular 5/8 socket hasn't got the insert. Also don't get carried away when you tighten the plugs down. They don't have to be super tight. Just tighten them down till they bottom out aganist the head.

I know what a plug socket is I use them quite often what happened was I had to use an extension and I put it in a bind leaning over my fender which put force in a diff direction than just clockwise thanks for the help tho! I love this site because of the quick responses

I understand Gavin. Just tryin to help and coverin all the bases.