Engine likes the cold

[Robert Buchanan]

Okay, here we go. Like many 3.2 engines mine has a rough idle that gets a little smoother when warm. The usual vacuum leaks are corrected, new idle control valve, adjustment to factory specs on throttle butterfly, all electrical tests are in range. Oh, and valve adjustment plus new 02 sensor.

For a while I have suspected the CHT sensor or the Warm Air Regulator as culprits. I have heard of no test for the WAR as it is vacuum controlled. CHT ohms are in range. I do know that the CO is slightly out of adjustment on the low side. So the engine is running a bit lean.
Dead stock engine, very tight, normal oil useage. 73.5K on the clock.

Last weekend the air temps dropped into the mid-forties here in South Texas.
On starting the engine, to my surprise the idle was perfect. Up to 1200-1300 or so and idled back to 900 or therebouts and off we went. Ran absoutely divine until the engine was warmed up (at first mark) then back to the slightly rough idle.

To make this condition a bit more pleasant I run around with my "closed throttle" electrical connection disabled. This allows the engine to run much better overall.

Okay, engine gurus.....anyone had this happen?

911_pilot