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Stumped with this rattle/shake problem

Ok, so I have a 2000 Dodge Grand Caravan, 3.0 litre, V-6, Auto-tranny, with 149,000 miles on it. I’ve had much repair work done lately, and have just recently installed new spark plugs, new radiator, new brake pads, new tires, ect. However, I’m still getting a bit of roughness on ocassion when I’m driving, its not quite, but almost a hesitation of sorts. Again though, this seems rare, and is not the crux of the problem(though I am still not sure why). I also am encountering a problem when I’m in drive, and drive only. It seems to rattle, with a vibration throughout the car at stop lights, stop signs, ect. I’ve tried sitting with it idle in Park, but it does not do it then, just in Drive, with the engine hot or cold, does not make a difference. Could someone help? I’ve taken it my normal auto-mechanic, but he was stumped, and I took it to the local Dodge delearship, and they told me that “dodge’s do that”, but would offer no explenation. Thanks in advance.

It sounds like you have a cylinder misfiring. The reason it doesn’t shake in Park is because the engine is totally disconnected from the drivetrain and the vibrations aren’t traveling through the chassis, and because there’s no load on the engine (in Drive the engine is still connected and the torque converter allows the engine to idle without overcoming the brakes).

Unfortunately, there are a whole host of possible causes. Perhaps a new set of ignition wires is all it needs. This is a distributor based system with wires and a coil pack, and anything in the high voltage side of the system is prime suspect. Wires, distrbutor cap, rotor, and stuff like that are all way overdue if they haven’t been changed yet.