I'm a certified GM and Toyota service manager and and warranty manager and the best
advice I can give is to look for a quality experienced installer. We have a lot of cars with
miriad problems (theft system, starting etc) usually show up a couple of months after
Christmas due to install concerns.
The defects are never with the product (modern electronics) but always with a shoddy
install. Stereo stores seem to hire a lot of temporary help around the holidays and therin,
many times, lies the root of the problem.
Those of you who are aquainted with a good installer are indeed fortunate. We have found
tiny wires that should have been delicately silver soldered and shrink wrapped simply stripped
back 2" and tied in a loose knot! The worst though is the use of Scotch Locks that work ok
for a few months and then suffer from fretting (fuzzy white corrosion) that causes varied
and intermittant problems.
One thing that users should also be aware of: If you're mindfull of your gas mileage, letting
a cold engine run in place on a bitter cold day really sucks the gas and an engine with no
load does not warm up very quickly. Letting it run in this situation for more than a few minutes
while you drink a cup of coffee, for example, is not thrifty.
Remember, the colder the ambient temperature, the richer the fuel mixture. When I was a kid
in the sixties, cars had a choke which choked down the volume of air entering the carburator
and made the mixture richer for starting in cold weather. Now days, your car's ECM (computer)
monitors the ambient temperature, coolant temperature, throttle position and the milivolt signal
generated by the oxygen sensor(s), among other things, to inject the correct amount of fuel so
you can take right off with nary a hiccup. On a zero degree day that mixture will be quite rich
indeed.