Nissan Repair: 1997 nissan problem, fuel pumps, mafs

Question
Just replaced the maf and trottle ps with a new sensors in aug.When it was they was bad it would not hardly run. The codes show the maf to be bad again. I thought the problems was only when the engine was cold but today it done the same thing after the engine was started back warm. The problem is for about the first 3 to 5 miles it will do one of two things. the idle will lope up and down lossing rpms each time till it dies or it will idle fine and not rev over 2500 rpms.. I mean it cuts off at 2,500 rpm let off it will run fine back up to 2500 . not at all like the last time the maf was bad and  runs fine after a short time.When it is acting up the exhaust smells different. 1997 4 cly. 4 x 4 any ideas?

Answer
Rick,

Sounds like the MAF is defective again.  In this short of a time it should be covered under warrranty.  I would ask for a Nissan unit this time to preclude problems in the future.  I do not know why MAFs and fuel pumps fail when they are non-Nissan parts.  But, they do and I have just gone back to factory units for both since I hate doing the same repair over again.