Ford Repair: 98 Ford Explorer - Stalling, positive crankcase ventilation, pcv valve

Question
I have a 1998 Ford Explorer that constantly stalls when first starting the engine. Once it gets going, it is fine. The check engine light came on after the computer was reset for the PA State emission test. My mechanic, who I do trust, said that the computer may be going or the timing belt may need replaced. Does this make sense? The vehicle does have about 380K miles on it, and runs well except for the stalling and the horrible gas mileage!
Two other questions..1) the computer always says low oil level, even though there is adequate oil installed...is this just a malfunction? Also the gas mileage is ridiculous...5 gallons only gets me about 85 miles! I used to be able to get a lot more out of her!  HELP ME! What can I do to get better gas mileage? (I just replaced the air filter, ehich was COVERED in oil - my mechanic said this could be because the oil is flushing through the carburator-is that possible? or is that from ricochetting off the roadways?)
Thank You!

Answer
Jocelyn-

  Well...I suppose this is good news, bad news time.  The good news is that I'm fairly sure I know a cheap and quick fix to your problem, which I'll get to shortly.  The bad news is that your mechanic is either trying to pull a fast one on you or he's so inept that he shouldn't be allowed around cars ever...not even to drive one.  First of all, while it's not impossible for an engine's computer to go bad, it's extremely rare.  Even then some lights on the dash would be the least of your worries.  The timing belt may need to be replaced, but it's not the first thing I'd ever suggest in such a situation.  As for the oil problem, here's the fix, a new PCV valve.  PCV stands for positive crankcase ventilation.  It's job is just that, to vent excessive pressure from the crankshaft.  If the valve gets clogged it can suck oil up into places it shouldn't be.  An oil soaked air filter is usually a pretty good sign that the PCV valve has gone bad since oil has been sucked up through the cylinders and pushed through the intake. It would probably be a good idea to have the spark plugs replaced, too.  If oil has gotten far enough up that it's coming out the intake, then it's gotten far enough up to mess up your plugs.  Oh...and as for the oil level light...the oil is still there, it's just being moved around the engine into places it shouldn't be.  Hope this helps.

Steve