My 2004 jeep grand cherokee has misfirein cylinder 6 and governor pressure 3# code. It has been misfiring at idle after changing from platinum plugs to copper core. I switched back to platinums and it got worse immediately. As it warms up it gets worse and worse to the point that it kicks in to limp mode. I have chaged the plugs, cleaned the pvc, cleaned the cranck case vent, cleaned the IAC. what is causing this?

Harvey N Tawatao

• 3854 Answers
• Posted on May 28, 2009

SOURCE: IAC Valve Location - 1996 Jeep Grand Cherokee

The idle air control valve is located on the back of the throttle body. It has an oval electrical connector and two torx screws holding it in. Unplug the connector, remove the two screws then lightly tap the body with a soft faced mallet to loosen it from the body. 
Once you have it out and prior to installing a new valve clean the seat inside the throttle body where the idle control fits. This must be very clean! Installation is in the reverse order. 
 To save some cash, pull the valve out and clean it with throttle body cleaner, this usually fixes the problem for quite a while.
Good luck and hope this helps.

SOURCE: 06 wrangler 4 cylinder... keeps going thru spark

Pull the plugs and compare them to the pictures in repair manual, ie: Chilton's or Hayne's. May be a bad injector flooding them or an intake leak causing a lean condition.

SOURCE: 2001 Jeep Cherokee with 6 cylinder engine -- PO306 code cylinder

Plug, plug wire, plugged or open fuel injector. are the most likely.

SOURCE: Spark plug gap for 2004 jeep grand charokee for

The spark plug gap should be posted on the emissions sticker under the hood. The gap setting posted on the sticker is good for all brands and types of plugs for your vehicule