1998 Ford Explorer

Engine Performance problem
1998 Ford Explorer 6 cyl Four Wheel Drive Automatic 150000 miles

This problem started gradually. The vehicle would be a little difficult to start, and would idle rather rough for 10-15 seconds before smoothing out and acting normally. If I gave it a little gas pedal, it would take a bit less time. Over a month or so, the time until it idled smooth gradually increased to almost a minute. No engine codes were given, weather not cold. The last time I got it started, it never did smooth out completely, and now it won't start at all. When I crank the engine, it coughs and sputters like it wants to start, but can't. If I crank it for very long, it often gives a very good backfire - popped the air intake hose off once. I've checked the primary and secondary resistance on the coil pack - it's fine, and there is spark to the plugs. There is plenty of fuel pressure. We just had our first child, and don't have a ton of extra cash to take this somewhere to get diagnostics done. If I knew the problem, I could handle fixing it myself, but without trouble codes, I don't know where to go next.
Timing maybe, or PCM?
Thanks much!
September 23, 2008.

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