A strange thing happened on the highway, heading to work, Tuesday morning. About halfway to work I had to accelerate pretty hard and afterward as I was cruising about 65, I noticed a vibration that'd never been there before. I immediately checked the oil pressure & it was normal. I have a AutoTap scanner on a Palm Pilot and it showed all cylinders were firing. There was no smoke coming out the exhaust. O2 readings looked normal and fuel injector pulses looked normal. Coolant temp was holding normal. I kept heading towards work and the longer it went the more it felt like a pulsation, not a vibration. At a stop light the idle would sag under 700 RPM then come back up. The engine never stalled and accelerated like normal. Under light acceleration the vibration seemed to fade away but holding a steady speed or idling the vibration is very noticeable. Ever since I owned it, when you shut down the engine, it made the infamous 4.3L V6 clunk-clunk. (GM issued service bulletins about it.) When I got it home, before I shut if off, I raised the hood to see if there was anything obviously wrong but didn't see anything. What I did notice was, when I shut the engine down, there wasn't any clunk-clunk. Is it possible that something happened to the balance shaft? Thanks for your time.
Friday, March 16th, 2012 AT 1:14 AM