chevy truck idle problems?

[Brian S]

My chevy truck idles up and down,if idles at all.When I start the truck it idles rough,but when you unplug the map sensor it idles fine but smokes out the tailpipe,Do not know what it could be,The engine light is not on,just replaced egr valve and idle air control valve,What could it be???4.3 liter vortec v6

 

[ramcharger]

i think it's the mass air flow sensor,but i'd get a diagnostic scan run to be sure. most nationwide auto parts stores do this at no charge with hopes of selling you the new part.

 

[bandit_60]

it could be the idle air control sensor. take it off and see if you can clean it.