Introduced in 1988, the Dynasty was Dodge's take on Chrysler's popular New Yorker sedan and one of the last K-cars ever offered in America. At between 2,900 and 3,200 pounds, the Dynasty was a svelte performer by full-sized sedan standards, limited mainly by its front-wheel drive layout but out-performing most vehicles in its class and price range. Chrysler had been continuously refining the K-car platform ever since it was introduced in 1981, making the late model Dynasty one of the most sophisticated and reliable of its family. These cars are known to last longer than many others of their time, but will require a bit of service from time to time.
Check your gauges first; they're your first line of diagnosis, especially for charging and cooling system issues. A voltage gauge that reads low at idle but rises with rpm indicates a bad alternator (also indicated by dimming and brightening of dashboard lights). A coolant gauge that rises at low rpm indicates a bad fan (which you should be able to hear at idle), low coolant level, blocked coolant passages or a bad water pump. One that rises under cruise indicates a radiator blockage, low coolant level or bad water pump.
Read the engine codes. The Dynasty uses On-board Diagnostics, Series Two (OBD-II), and can self-diagnose most engine and transmission problems. Most chain auto parts stores have a code-scanning tool that will read any active codes (those that cause the check engine light to stay on), but won't read stored codes. You'll need to take the car to a garage to read stored codes.
Listen for any strange noises coming from the engine, and locate the source. A loud, constant squeal may indicate a slipping belt; a quieter, more high-pitched squeal may indicate a bad accessory-drive bearing. A hard clattering coming from the valve cover may indicate a collapsed lifter, worn out rocker arms, damaged valve spring/retainer or bad valve; a softer rapping from the fuel injectors indicates a problem there. A loud knock from deep in the bowels of the engine indicates worn or damaged bearings.
Use a multi-meter to check sensor output. Automotive sensor technology circa 1990 wasn't what it is today, and sensors are typically some of the first things to go on these cars. Check throttle position sensor (TPS), oxygen (O2) sensors, manifold air pressure (MAP) sensor, crankshaft position sensor (CPS), knock sensor, coolant temperature sensor and transmissions fluid pressure/temperature sensor. Use your digital multi-meter to determine if the sensors' voltage outputs fall under the various ranges specified in your reference book.
