135,000 miles, well maintained as in I've owned it since new. Started bucking on startup, intermittent at first, now more consistently. Put on a new starter, same thing. I suspected head gasket but pulled plugs and there is no coolant in the cylinders at all. Small coolant leak at the back of the intake, but no coolant in the oil at all. I'm beginning to think it is one of the "sensors" but have no idea where to look. BTW, it throws no codes
But if the knock sensor was whacked, could the ECU be advancing the timing to the point where it would buck?
Once it starts, it runs just fine, makes good power and generally acts normally.
Am I condemned to take it to the GM dealer?????
