99 Sonata Hesitation

Late last summer I posted about my 99 Sonata (2.4L) hesitating badly when started cold. It never actually cut off but came close. When warmed up it ran fine. There were no CEL indicators. Most responses were to try injector cleaners. HyundaiTech also mentioned what it may be caused by and commented that if that was the case, then the problem would go away in the cold weather. What I just said is best that I recall, I have searched and tried to find that post/response but can't. On two different occasions, I put Chevron Techron cleaner in the tank and all winter it has ran fine when started up cold. I thought I had solved the problem, but how that the hot weather is back, it is coughing and sputtering again when started up cold. Runs fine when warmed up. HyundaiTech, do you remember what you may have thought the problem is and how to correct? thanks