Hello everyone. Just bought an 06 1500 4.3 liter in Atlanta with 98k. Drove it to Virginia and noticed the temp never got above 150 or so. Changed the thermastat, plugs, wires, rotor and cap. Fired it up and it hesitated for a few seconds then cleared up. Now it finally runs at temp, but I notice a very slight rattle when accelerating uphill. It doesn't sound rhythmic, and at first thought it was a spark knock, loose heatsheild or a failing cat. I didn't notice this noise before the tune up. Who knows how long it was run with the thermastat stuck open before I bought it.

I understand that running it cold can increase carbon buildup. I think I'll try seafoam or gm top end treatment, but wanted to get some opinions on what others might think could be the culprit of my light rattle after being run with an open thermostat for an extended time. Any ideas?

 

Could be a spun rod bearing.....could be ignition timing issue....could be exhaust rattle....