Here is something I stumbled upon today while changing my IAC on my'99 3.9. After changing it the truck acted like it had a sticking throttle for a few moments, then it would settle down. I figured the new one may be defective so I put the old one back in. Same thing. So I put the new one back in and dis-connected the battery to reset the computer and it works great. I am not 100% sure that did the trick but it works now anyway. This was not mentioned in the insructions or the clymer manual. I hope this will be of some help to someone.