2001 Taurus Sel Duratech

I have a 2001 Taurus SEL w/ Duratech engine–When idling in drive at a light or similar situation, the idle gets rough and the check engine light comes on—when my mechanic kicked the code, it said problem with # 5 cylinder–Switched plug and wire with cylinder next door and same problem with # 5–Now, the kicker is that it clears up on its own and runs smooth as ever. I know about carbs from my youth and we used to have a problem with the needle valve picking up dirt, but I can’t understand that if it is some type of debris affecting the EFI, why is it only affecting the same one cylinder–Hate the Elect. trans and overdrive also in this car

While you’re playing swap, swap out #5 fuel injector with another position. Result?

And check the compression while you’re at it - all cylinders, but esp. look at cylinder 5. How many miles are on it?

Thanx–52,000 miles–99% of the time it runs like a champ