My 03 cummins has a rough idle hangs at 1200 rpm and won't fall on less u put it in gear and release the clutch hard to start in cold weather and smokes more than normal any suggestions would be great its my first Deisel and I don't know where to start

 

Idle issues can be associated with the throttle position switch on those trucks. Do some searching and you will find a lot of information on trouble shooting the TPS. There is a process for making the truck "relearn" the TPS, but it only lasts a little while. The smoke could be associated w/the truck idling poorly due to this issue.

The hard to start and smoke can be either an issue with the intake air heater (grid heater) whcih is located where the air horn meets the head on top drivers side of the motor. Its an electric heating element that the computer turns on when the temps are low . . .it heats the incoming air when you are starting it to help it ignite the fuel easier.

The hard to start and smoke can also be related to worn or damaged injectors. The early Common Rail motors had more injector problems than the later ones.

While the "wait to start" light is on, the grid heater should be actuated. You can check the voltage on the heater while the WTS light is on and make sure the relay is working, you can check the resistance of the grid heater and check its continuity to ground (resistance from the grid heater to ground should be 0 because its dead shorted to ground).

Also, check your batteries and make sure they are good. The grid heater puts a pretty good load on the system as does turning the engine over and sometimes that can make the truck not spin quick enough to start . . .but that won't cause excessive smoke.

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BTW, you can also do some checking locally to find a good dealer that does a lot of diesel work . . .find one who services larger trucks and that usually a good start. If you are at a complete loss of where to start, spending a few hundred $ to have someone w/a scanner go through the truck and diagnose your issues and do cylinder contribution work and injector return tests can be a lot cheaper than throwing parts at the truck . . . especially if you start talking about replacing fuel system parts. You don't have to let them do the repair work, or buy the parts from them . . .but they can point you to the problems so you can fix them yourself. Just a thought . . . and it needs to be a reliable dealership/shop who knows diesels . . . if they don't knwo diesels, they may do more harm than good.