My '93 240 with 106K has some idle hunt issues that I'm a bit stumped on:

Symptoms:

-When cold there is some bounce to the idle of +/- 250 rpm or so.
-When warm, idle seems to drift slowly +/- 50 rpm.
-Idle also seems just a little rough, especially when cold.
-Difficult hot start unless I press the gas a little.
-Vacuum shows 15" with some unsteadiness.
-Occassional stalling

What I've checked:

-Cannot find any vacuum leaks. Intake gasket and throttle bottle gasket are new. I verified that the brake booster is not leaking, by pinching the hose. Local shop did a smoke test and found a cracked flamed trap, but that's been fixed. I did a propane search as well.

-New plugs, wires, cap & rotor, fuel filter 15K ago.

-Cleaned IAC valve 15K ago. It does click during the LH2.4 self-test, but I wonder if it is sluggish.

-New ECT sensor

-New Fuel Pressure Regulator

-O2 sensor voltage does oscillate between 0 - 1 volts, but if I create a vacuum leak to takes at least 10 seconds to begin oscillating again. O2 sensor is original.

-Cleaned Throttle body 15K ago. Adjusted linkages.

-Timing looks good.

-No CEL codes.

-CAM timing advanced +5 deg with VX cam

-Valves adjusted 15K ago.


Any ideas?