So, the suburban started doing this bucking thing between 1k and 2k rpm, but drives smooth above that. It also seems to happen only after the engine is up to full temp, after about ten minutes of driving. It will go away if the engine has a chance to cool down before driving again. It also doesn't buck when the rpm is going back down through the 2k to 1k range with my foot off the gas. But then, going back up through that range, even with the slightest pressure on the gas, and it bucks and shakes until I get above 2k... then it drives fine! I recently had the timing chain replaced and I have almost 200k miles. I was wondering if it's something like a crank sensor getting heat-soaked, or if it's timing/distributor related, or if it's torque converter lock-up related?!? I don't think it's fuel delivery related at this point. Anyone else experience this? - - - Updated - - - hmmm... Not a good sign, if I have 73 views and zero replies. I'm guessing that means nobody has a clue as to the source of this problem.