Engine runs rough at an idle when warm. RPMs unstable at cold startup. Runs fine at road speed with the occasional "hiccup." More prevalent whe the gas tank is 1/2 full or less. Runs fine with the gas tank 3/4 full or more. New fuel pump and filter, gas tank is venting properly. First thought was intake manifold gaskets, but why woud the fuel level make a difference if that was the problem? I have yet to get the codes retrieved. Hopefully I can get that done next time I have it in town. TIA.
Cleared out the codes and P1400 remains. Looks like I'll be cleaning the EGR valve, checking the tube and orfice for blockage, inspecting the harness connection and probably end up replacing the DPFE sensor.
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