hey i have a 3.4 L with 193000 miles on it and im starting to hear a knocking noice at low rpms... like at around 1000-1500. im also hearing something really loose when im idling. my friend said it sounded like the bearings on the piston shafts. is this a bad problem, is it easy or hard to fix, and is it an expensive problem? any advice would be very appreciated.

If it is what your friend says, then it's very bad. However, those seldom go bad with those low miles. . Without hearing it, I can't say what the cause is, but I would start looking before it gets worse. When is the last time you had the timing belt replaced? I shredded belt can make a noise like that. I also had a knocking noise that I thought it was a bad piston bearing, but turn out to be a $40 timing belt tensioner. The flapping timing belt made a knocking noise.

I probably have the same problem on mine. I have a 2006 V6 4.0 with about 45000 miles. Mine makes a lugging noise between 1500 and 1800 rpm. It does not stop unitl the torque range increases which is around 50 mph...I would like to know what this problem is as well before it is too late...