I have a 2002 Trailblazer that is running rough. So far I have replaced plugs and coil packs, map sensor, cat converter, and both O2 sensors. Still idles rough and acts like its missing. Any ideas what to check out next?

 

When does it start to run rough?(during idle, low speeds, higher speeds)
Does it throw up any codes?

 

Runs rough constantly but is more noticble at low rpm especially at stop lites etc. The service engine soon indicator flashes intermittently. Will be taking it to the shop tomorrow to check out what codes it may have.

 

loose or broken vacuum hose causes rough idling, and is the easiest repair of all.