07 cadillac cts 3.6, 48000 miles, first day, purchase vehicle wouldnt start ( bad battery and alternator} running rough at idle skipping ( misfire) and loss off power on highway( blamed battery), one month later and several dealer visits, new water pump and thermostat, also still running rough at idle loss of power and now major spark knock, told to try better gas and additive and wait for an engine code, NOW engine code p0021 "excessive cam play " told by dealer that cadillac knows of the problem and its due to a timing chain not being built to specs!!! correct me if im wrong cause im not a mechanic but poor timing means nothing works in the exact order its suppose to causeing excessive wear on parts that normally do not wear in 40 thousand miles, theyre solution shim the cam( yup tempory bandaid fix) every other mechanic on the planets fix, change worn bearings, head, timing chain and cam, and hope to god theres no major damage to other parts of the motor running it till they do finally fix it right !!its true the squeeky screaming fit really does get the grease, its in shop for what we are being told is a total motor rebuild, do not settle for anything less, ill say it again cadillac knows this is an issue