Right now the way the weather is changing here in California (temp in the 30's) you and your truck are not used to that cold...................it takes 4 or 5 long runs just to get the heat up to normal in your truck and if you putt around it will get to cool to run well. Don't know if thats your problem but I've had about 5 customers in here thinking there engine was bad and its just to cold[&:]