Nissan Repair: 1999 Nissan Sentra starting trouble, nissan sentra gxe, nissan sentra

Question
I own a 1999 Nissan Sentra GXE which has done about 58K miles. In the last month or so, I have noticed a peculiar problem. When I try to start it after it has been sitting idle for several hours (like overnight), it just sputters and dies out - unless I crank it up and hold for about 15-30 seconds. I've had it examined at the mechanic shop, but the same problem persists even after I've had the starter, spark plugs, rotor and distributor caps replaced, and the fuel injector system cleaned. I emphasize, this starting problem appears only when the vehicle has been idle for several hours (like 4-5 hours). Once I get it started (after cranking for 15-30 sec), it doesn't stall while driving, and the start-up is good for the next few hours. The mechanics seem a little clueless (nothing wrong with them, they're good), and this is getting frustrating. I looked up Nissan and there aren't any notices or recalls posted for this type of problem. Car has a good history and battery's not a problem. Never had any serious trouble before. Any tips and suggestions would be helpful. Thanks.

PS. Car was bought when I lived in Pennsylvania and now I am in Colorado (~2 yrs). Could the altitude be a factor ? But this problem is very recent.

Answer
Kumar,

Several things could cause the starting problem.  The first is the throttle body needing cleaned and the second is the temperature sensor that tells the computer the car is cold.  Since you did the plugs fuel cleaner and such I would assume the injectors are not sticking.  That could be one of the problems too.  Yes, have the injectors checked for leaks.  That is, get a pressure gauge for the fuel rail and screw it into the fuel rail and then start the car.  Now, turn the car off and see if the injectors hold pressure.  You could ask the person that changed the plugs if they noticed one or more that were really black as opposed to the others.