I have a jumpy idle when my car has ran for more then 30 mins and then sits in traffic. After about a minute the idle jumps to about 1200 rpms or then back down. I have replaced the IAC motor four times, but not with Delco replacement. I read another thread and it said that the IAT sensor could be the cause. It would make sense since it may just get heat soaked with no air going by it in traffic. Any other ideas guys? It goes through all rpms smoothly right now. ANy help is greatly welcomed.