I own a 2001 Lumina sedan with 65,000 miles on it's 3.1 V-6. I bought
it as rental return about five years ago, and have put about 45,000
miles on it, and I generally take good care of the car. The problem is
that when the engine is cold, I have a fairly loud tapping noise
(moreso than a click) coming from the motor. It is hard to pinpoint
the location, but it is not in the immediate area of the rocker arm
covers. It's loud enough that I like to let the car warm up some
before I drive it. Typically the motor is quiet when it first starts,
but then it gets noisy in less than a minute. It settles down after
the engine gets to full temperature. The car drives fine. I have been
told the engine is a bad design. Motor oil brands and types
(synthetic) do not make any difference in the smoothness of the motor.
I am reluctant to use additives. I need to keep this car, but I am not
familiar with the workings of the valve train or lifters, etc. If
someone is has had some experience with this motor and can offer an
opinion or conjecture, I would appreciate it.