Mitsubishi Repair: 1992 2.4L engine vibration, spark plug wires, couple teeth

Question
I have a 1992 Dodge Ram 50 with a 2.4L mitsubishi motor. One cold morning I went to warm up my truck, a little later I drove off and felt a vibration and it lacked power when taking off.  I deduced it was coming from the engine, and check the mounts, there fine.  Had the timing belt replaced a year ago, that's when the technician told me about the "silent shaft belt".  I tear into the timing cover expecting to find a broke balance belt; but it's still in one piece, with the all the "teeth".  What else could it be?

Answer
Scott,
Usually when the timnig belt is replaced, the silent shaft belt is also replaced.  But even if your silent shaft belt is completely intact, it's possible the tensioners for your timing belt or silent shaft belt have failed and caused the silent shaft belt to slip a couple teeth.  This would be enough to cause excessive vibration and low performance.  Though before you get into replacing any more belts or tensioners, you may want to consider a regular tune-up. If it's been more than a couple years since you've replaced your spark plug, wires, and other maintenance related ignition parts, you should do so.  This is good practice even if the tune-up doesn't help with your vibration problem.
Good luck!