rough idle, power loss, CEL, misfire #3 - HELP!

[erinmahoney04]

2002 Envoy SLT, 4.6 v6.

Started idling rough, check engine light came on. Ran the computer on it, told me we had a misfire in #3.

Replaced plugs, Plugs 3 and 5 were very dirty, even oily. Replacement plugs did not help immediately. Next day, started it up and it ran fine for 1/2 a day, then reverted back to the rough idle, loss of power, blinking Check Eng Light.

Any ideas? HORRIBLE gas mileage right now, cruise control won't work either.

Thanks! can't afford to drive it like this for long with high gas prices...

[maxwedge]

Could be bad coil/s or dirty injectors, this must be checked on site, no quick answer for this, switch coils with a know good cyldiner see if the miss moves.