Dear Ronev,
See if the following synopsis of temperature dependent engine conditions pertain to your vehicle:
COLD START – ENGINE NOT OPERATED OVERNIGHT – 40 DEGREE AMBIENT:
Upon cranking engine starts right up and the idle jumps to about 2K. Then it starts idling back to about 500 rpm then it jumps down to about 300 rpm and almost dies and then it settles down to a rough idle. This process lasts approx 15-30 seconds.
COLD START – ENGINE NOT OPERATED OVERNIGHT – 30 DEGREE AMBIENT:
Upon cranking engine starts right up and the idle jumps to about 2K. Then it starts idling back to about 500 rpm then it jumps down to about 300 rpm and almost dies and then it returns to about 2K and the cycle then repeats. This process lasts approx 2 to 3 minutes before settling down to a rough idle.
COLD START – ENGINE NOT OPERATED OVERNIGHT – 20 DEGREE AMBIENT:
Upon cranking engine starts right up and the idle jumps to about 2K. Then it starts idling back to about 500 rpm then it jumps down to about 300 rpm and almost dies. At this ambient temperature the engine acts like it is running on 4 cylinders; it sounds like a Harley V-Twin and the truck shakes violently (approximately 4 to 6 inches of side to side movement measured at the roof). It returns to about 2K and the cycle then repeats. This process lasts approx 10 to 15 minutes before settling down to a rough idle.
WARM START – ENGINE OPERATED WITHIN LAST 2 TO 3 HOURS – ANY DEGREE AMBIENT.
ALSO - COLD START – ENGINE NOT OPERATED OVERNIGHT – ANY TEMPERATURE ABOVE APPROXIMATELY 40 DEGREE AMBIENT:
Occasional extended cranking to start. Rough idle.
If any of the above sounds familiar you can tend towards the lower intake o-rings leaking. As to your recent issue of an idling issue once engine has reached normal operating range; i would respectfully suggest repair of the original fault condition (o-rings change out) before pursuing and further troubleshooting in this area. Is it possible for the o-rings cause complete idle failure? Yes. Likely? No.
To ensure your sense of humor remains: I recently stumpled upon a rather interesting diagnosis by a Ford Dealership (read "group of male reproductive genitalia") upon an "x', with 56k onboard and similar symptoms to yours and the above. The above captioned "group" decided the customer may best be "serviced" with a mere $700 being invested with them, for a work scope that included intake manifolds removal (as with o-rings change out), allowing them access to the rear side of the intake valves, of which they were to clean. Apparently, according to their diagnosis, the rear side of the intake valves were "choked" with carbon build up. Said build-up was responsible for soaking-up such voluminous quanties of fuel/air mixture that engine supply deprivation was the route cause of all ills.
Anyway, change your o-rings and check out your IAC isn't sticking (soak the mechanical mechanism in carb cleaner (ensure the cylindrical shaped solenoid is not).
