Blazer Forum - Chevy Blazer Forums - 2 Things: Vibration, and Hesitation

2000 2DR Blazer 4x4: 112,000 mi.

I have two issues. First is a front-end vibration. I feel an extremely mild vibration, at modest cruising speeds (40-50 mph). It is heavily amplified when applying the brake. It turns in to a shudder when the brakes are pressed.

Two months ago I had the front left wheel bearing replaced. The truck rode like a dream for about a month, and then the vibrations began. Subtle at first, and only when braking. Recently i've noticed the very mild vibration while moving, and it's heavily prominent when braking.

I got new tires and brakes (ceramic) installed last May (5/07), and the rotors were turned at that time as well. My mechanic thinks the rotors may have warped. I'm not so sure:

One symptom of my wheel bearing needing replacing was a creaking sound. Kind of like a dried out hinge. The bearing would creak while the truck rolled softly to a stop. I have heard similar creaks since the vibrations began. Only a few times, and not as frequently as with the bad wheel bearing. Could my vibrations be coming from my new wheel bearing? The sound came from the same wheel (front left).

The other thing (which is unrelated to the vibration) is a hesitation on acceleration. When the truck is cold, or has even been sitting for an hour, the initial acceleration is very weak. If I press the gas down, i must do it gently, and slowly accelerate. VERY slowly. If I were to press the gas normally (as if starting from a front position as a red light turns green), the engine does not receive power as it should. It's almost like it's about flood out. Again, this is when the truck has sat, not running, for an hour or more, and at it's worst when it's sat overnight.

I've gotten in to the habit of letting the truck run for at least a solid sixty seconds before putting it in gear and moving. and I still take off gingerly. Once the truck has been moving for a mile or so, or the engine warms up, acceleration from a dead stop will normalize. My mechanic suggested a tune-up, but could not directly answer why the truck hesitates. He's good with repair, but not the best with diagnosis, as far as my truck has gone. He didn't think inititally that my wheel bearing was bad, but admitted it was when he replaced it.

Any help or suggestions would be appreciated. I can elaborate more (on both issues) if needed.