5.4 engine miss under acceleration
I'm dealing with an intermittent engine miss when under acceleration. I swapped out a blown 5.4 engine (145k) in my 2001 expedition. I swapped in a 85k mile 5.4 from a running 2001 Expedition. I was able to drive the donor vehicle prior to pulling the engine and it ran just great. Thanks to the help of this forum, I did the engine swap by myself in our driveway (a Bear).
Since the swap ( a year ago), I have an occasional miss in the engine. It flares up when I let off the gas (for example coasting down a hill) then get back on the gas. It will also happen if I stab the gas pedal or attempt to accelerate heavy as when merging onto the freeway; It runs good for a couple of seconds, then starts falling on its face.
If I feather the heck out of it, and drive like a Granny, it will never miss a beat. It pulls our 4500 lb. travel trailer no problem-as long as you feather the gas.
I just had the vehicle smogged (CA.) and it passed all tests with flying colors. No "check engine" light has ever come on. It's a 2nd family vehicle that gets driven only about once a week, but I'd like to get it resolved. I'd really appreciate any input you folks may have. Thanks.