My truck is a 2005 with the Duramax Diesel & 6sp manual. Normally, it
idles about 750rpm. Occasionally, the idle speed will drop to 675 rpm
or so and the engine will shake terribly. Lightly depressing the
accelerator will return things to normal. Fuel economy is great for
this size truck. I get about 24mpg cruzing empty on the interstate at
57mph. The other end of the range is about 11 mpg towing a 14000 lb
5th wheel through the mountains.
I have checked for codes when this occurs and none have been found so
far. I keep checking everytime it happens. As expected, the truck
always idles normally when I stop by the dealer.
The only idea I have is possible water in the fuel. I am currently
using a fuel conditioner recommended by the dealer. Maybe this will
work.
Does anyone have any suggestions?
Dave
