dodge is known for fuel pick up issues. the fuel sender unit has low voltage. change that and fuel filter. nnot an easy fix . because both are in fuel tank.
Try checking for the crankshaft sensor
jerking speed 40 50
Your question is very confusing. If the car runs then it has to start. Please clarify.
Possibly a vacuum line came undone
If your dodge diesel runs rough at 2100 RPM it is probably starved for fuel. Have the fuels filters changed and / look for an air leak in the fuel system. My 1996 had rusted fuel lines on the top of the fuel tank. cost about $600. Canadian to repair.
temp senser or spark coil
There are several things that can cause your 1999 Ford Crown Victoria to idle rough when it is cold. The most common cause is a leak in one of the vacuum hoses.
try checking out the coil pack
Yes. the computer runs the cruise.
Depending on how far off, runs rough, check engine light, no start, engine damage.........
a pile of poo