99 Jeep Cherokee Runs Rough When Cold

I just purchased a 99 Jeep Cherokee and it spits and sputters, seems to be starving for gas when it's cold. Within 3 or 4 minutes it warms up and runs great. I brought it to my mechanic, that I have full trust in, and he hooks it up to his Snap-On scanner and it shows no problems.

I had brought him a different vehicle with similar problems and it turned out to be the oxygen sensor...which he replaced and problem solved.

I reminded him of this and he insists the scanner would pick this up so it must be something else. He thought it might be the coolant temperature sensor but he'd have to look into this theory a bit more. Hoping someone may have come across this same issue.

Im having the same prob wiht my 91. when cold the engine light will come on it will cough and sputter, once it warms up it goes away... except my problems are getting worse and more random, such as alternator stopped charging temporarily, when scanning it it resets the scanner when u touch the gas...... Ghosts:runaround: