I have a 1999 Blazer which runs very well during the winter but when the weather warms up or even when it is cold and I drive on the highway for a while and warm it up well, it starts idling rough. WHen I begin to accelerate it smooths out but when it goes back down toward idle at a stop, it starts running rough again. There is no check engine light coming on or engine codes and the check engine light does work. Someone suggested it could be a bad ignition module but I have not swapped that out. The key is it is when it is warmed it up it happens. Any thoughts and thanks.

 

did you check the fuel pressure? check this link out for more information on testing the fuel pressure
https://blazerforum.com/forum/tech-a...agnosis-23038/

whens the last time you did a tune up ?