Car has intermittent starting problem

Description of symptoms: Every so often, car will not start. Commonly this occurs about one in four starts, but may go days between problems, or the problem may occur twice in two starts. When vehicle does not start, it will crank over fine, but will not fire. Waiting for 15 to 90 minutes (sometimes as long as three hours) will produce a start. The car may or may not become flooded, but after repeated tries, there is a gas smell. I then push the gas pedal to the floor (disengaging the fuel pump) and try again. This does not result in a start, but may within ten minutes or so (or may not). The car also experiences occasional “flameouts”, that is the engine will kill as I am driving down the road, and will usually not start for about 15 minutes to two hours (but sometimes starts immediately). The car always starts well in the morning.
This may or may not be related. In cool or cold weather, if I do not warm the car up it will chug down the road with great difficulty attaining any speed for about a minute.

Things to note: When it does start it starts well. When operating, the engine runs smoothly. The idle is smooth. The engine runs well while driving. It actually runs so smoothly and quietly it may be difficult to tell if it is running. It sometimes “hiccups”; that is while driving I will experience a momentary loss of power. This loss of power lasts no longer than a half second. Once, early last summer, the loss of engine power became acute in that I could suddenly go no faster than about ten miles per hour. I stopped at a gas station, and it chugged and sputtered for some five minutes before it suddenly began running well again. This has only happened once.
It sometimes seems as if it may be hesitating or at least be wanting to pull back, but this may be another (a brake) problem. There is an occasional smell of gas.


Things I have done or have had done:

I have replaced the following items:
• Fuel filter
• Fuel pressure regulator with rail assembly
• Air filter
• Spark plugs
• Ignition Control Module with coils
• Fuel Pump
• Computer

Other: I have had the fuel pressure checked... It checked fine.

What I have been told thus far: I have spent the better part of the year trying to puzzle this out. I have been told by several mechanics that the car is “a time bomb”; that as long as it is behaving, everything will check out fine, so there’s no way to check unless it misbehaves while in the garage. I have been told it was most of the above items, but it was not. I have been told it was the fuel pump relay (and told if the relay was not working properly it wouldn’t be intermittent that it would simply not work). I have been told it is the fuel pump (and also told that if it didn’t work it would not be intermittent) it was replaced. I have been told it might be the O2 sensor (but an internet search of O2 sensor symptoms did not match). I have been told it was some kind of “exhaust gas sensor” (supposedly located near the harmonic balancer). I have been told that it is probably fuel related. I have been told it is probably electrical.
Recently, having generally replaced the entire fuel system, it has been definitely established that when the problem develops, I am getting no spark. Since replacing the computer, the problem, although it still exists, seems shorter in duration (15 minutes rather than an hour or more), although this may be due to the cold weather and may only mean that whatever is malfunctioning, it cools faster. I have noticed better performance since replacing the computer.

I have noticed another symptom which may be unrelated. Before the malfunction occurs, my temperature gauge will read over 200 degrees. The engine may or may not experience a little rougher idle.

New: I have now been told that the problem is the “camshaft position sensor”, or possibly the “Camshaft position magnets” or even the “crankshaft position sensor”. I have also been told it might be the O2 sensor. As of December 2010, when the problem occurs, it will always take two to three hours before it starts. The problem occurs nearly every day.