I have a 2001 Lincoln LS 2 Door V-8 with 66,000 miles. When starting the car after it has not been started for a couple of days there is a loud noise similar to a "backfire" from the left side under the hood. The car will then start and run normally.

Welcome to the forum!

Noises over the Internet are one of the most difficult things to diagnose, therefore requiring a lot of description.

First off, when you say "Left side" are you referring to as looking at the engine from the open hood (passenger side) or from sitting in the car (driver's side)? Have you been looking under the hood when the noise occurs? If so, does the engine do anything odd when the noise occurs, such as shake abruptly? Does the noise occur as soon as the starter engages, or is it after a revolution or two of the engine? Does the enhaust smell odd? Are there any diagnostic codes? Has the fuel economy changed recently?

-Rod

Thanks for responding!
The noise comes from the drivers side and occurs as soon as the starter engages. I have been looking under the hood when this occurs and did not see an engine shake or notice an odd smell. I have not noticed a change in mileage either. I had been told it may be due to a faulty coil on one of the cylinders but there are no engine codes and the car seems to run ok.
Thanks

If a faulty coil, I would expect the exhaust to have an odd smell and, as you mentioned, you'd notice it when having the engine under load. I wonder if there's something loose in the starter motor since it sounds like that's the only time you notice the sound.

-Rod