My truck's idle speed has varied greatly lately. It usually idles around 800 rpms, but on certain occasions it has run as high as 1100 rpms. This is after the truck has heated up and been driven for a while. The truck has only 3000 miles on it and my fuel mileage has dropped lately(shouldn't have winter blend fuel in southern Oklahoma). What is the standard idle speed and what could be the reason for this problem? Thanks in advance.

 

Possibility that you have developed an air leak in the fuel lines or system, do any changes lately to the fuel system. Check out any diesel leaks on engine.PK

 

First, this isn't the cold weather fast-idle feature kicking in, is it? <br><br>If not, the high idle is probably due to a bad sensor. Either the APPS/TPS (accelerator pedal position sensor/throttle position sensor) is (in error) telling the ECM that you're pressing the accelerator when you're not, or the sensor that the ECM uses to detect engine speed is not working properly. I'd check the APPS first.