I have a 1993 Eclipse with a 1.8 liter engine and auto trans. It is completely stock, no modifications of any kind. The car runs fine except the idle is a little rough. The engine idles at about 750 rpm. The problem with the idle is the engine acts as if it misses every now and then. Its not serious enough to stall the engine, but it is noticeable. I guess you could say the idle stumbles a little.
Ihave noticed that before the engine warms up, the idle problem is mostly unnoticeable. Once the engine reaches operating temp the erratic miss occures. Note that when the engine is cold, it idles faster which helps to minimize the engine miss. Also note that there is no back fire when the miss occures. It is as if the power for the ignition was suddenly shut off for a split second, just long enough to cause the miss. There is no discernable pattern to the miss. It seems to be completely random. Also when cold, sometimes when I try to accelerate to fast in drive, from a dead start, there is a back fire through the intake manifold. That only occures when engine is very cold, just after start-up. Maybe that's normal? or not...
I have checked the plugs, plug wires, ignition timing, timing belt and settings, idle control motor (it checks out good resistance wise and in moves smoothly and completely with 5 volts applied to it), the PCV valve is good, the throttle body has been cleaned and inspected, I have checked for vacuum leaks and found none (maybe Imissed something), there is no EGR valve, the distributor cap and rotor are new, I have tested the power transistor and coil in the distributor, the engine, head and tyranny all have been rebuilt approx 1,000 miles ago and I installed a new air filter. The balancing shaft belt is new and the shafts timing was adjusted when the engine was assembled. I have check functionality of the oxygen sensor and the intake air temp sensor in the air flow meter. Both check out good. Have used an oscilloscope to view fuel injector pulses, ignition pulse, TDC pulse and used an old MAP sensor to display the vacuum levels in the intake manifold. I could not find/see any glitch or bad signal that coincided,with the engine miss. About the only things I have not checked are the air flow meter, the barometric pressure sensor in the meter, (don't have the instruments to check these),the fuel pressure regulator, fuel filterand the fuel pump. But if any of these components are bad you would think it would display symptoms at all engine speeds.
Any suggestion would be greatly appreciated.

Thanks
Scott