Thank you very much, Tracer, for your response! Well, I don't believe that I have ever experienced misfires or understand what they are really. If a cylinder is not working or is not in sync with the others, I couldn't tell you. I'll go further into detail
about what I have experienced. Shortly after I bought the car, Nov. 2007, it started to smell of gas (not exhaust) in the cabin. The smell was unbearable! I took it to a local Midas and they fixed it. Turns out that a fuel line wasn't fastened and gas was spraying everywhere under the hood! They just tightened it back up and that was it. They had no idea how it could have gotten loose in the first place! Shortly after, the service engine soon light came on. Poor acceleration, sputtering from the engine followed. It just didn't feel smooth like a Cadillac should. One year before I owned this car, I had a 1994 DeVille which had nearly 50k more miles then the 1995 DeVille I have now and I didn't have these problems with the 1994 DeVille. Besides the one year difference, it's practically the same car! (Both are Sedan DeVilles with the 4.9L)
With my 1995 DeVille that I have now, I have recently replaced the water pump because coolant was spitting out from the seal/gasket! I also had a new exhaust system put in because I smelled exhaust outside the drivers door when I stopped at stop lights with the window down. The smell wasn't as strong as coming straight out of the tail pipe. I had the exhaust pipe, universal catalytic converter, muffler and tail pipe all replaced with new. Now I just smell less toxic exhaust outside the driver's door when I have the window down which is unsatisfactory and nauseating. I don't know where else the exhaust fumes could be coming from? With the windows rolled up, I smell nothing.
Anyway, the engine performance; It just doesn't purr like a one owner car should. (Cosmetically, the interior and exterior look as though my 1995 car is only five years old at the most! Along with the low mileage, I don't believe that I should be having these issues!)
The problems I have are sputtering, hesitant acceleration and over all poor or lethargic performance. These problems don't occur all the time, but they do occur frequently. While I am accelerating, maintaining speed or when I stop and stand at red lights, the car shakes/ gyrates. With small adjustments of the gas pedal, either to increase or decrease speed, the problem will settle down or go away. When I drive in residential areas I can experience the same problems. When at a stop light and at a stand still, the car will shake/ gyrate. At a stand still, the car can shake and won't stop until I accelerate to a specific speed. The shaking/ gyrating can be strong to mild. Other days, it seems that my car thinks that it's a sport coupe! My car can be a beast and I can pass others so easily when on the express way or residential streets when my car isn't acting up. So you see, it's not like my car constantly runs like crap, it's at certain moments. Also, the service engine soon light will come on for a half day, a few days, then won't be on at all for a while.
I live in Illinois, so for the winter, I let the car warm up before I drive, usually no less then ten minutes and some times more depending on the outside temperature. I switched the car to 100% sythetic when I first bought it, but recently had to switch to regular because the local lube shop raised the price of the synthetic service by $15.00. Even on the synthetic, I experienced these problems. I also lose a quart and a half of oil every 900 miles.
Please help! I really like and would like to keep this car! If I sold it in it's current condition, I couldn't get enough money to buy a good car!