Cadillac Repair: cadillac, spark plug wires, cadillac sts

Question
hello.  i have a 1995 cadillac sts and it is running bad. it runs even a little worse when the service engine soon light is on, but it isnt on all the time. it usually goes away when i restart my car.  the car can sometimes be hard to start but it always starts. it seems like if i restart it after just driving it that it starts up better. the car idles very roughly when at a stop and the car jerks and shakes when i first give it gas but the higher the rpm the better it accelerates. it also smells like heavy gas. i already replaced the spark plug wires and the map sensor because my friend did a diagnostic on it and it said the fuel system was too rich. do you think it could be the fuel filter? any ideas?  i appreciate any help! thanks

Answer
Hi Kurt, I'm going to need alittle more info so I can give you an educated answer. Do you have the northstar engine or the 4.9 liter? When you have the engine running in park does the service engine light turn on or after driving awhile does the light turn on? After the light turns on pull over to a safe location, put the gear selector in park and with the engine still running push and hold the off and warmer/red button on the climate control panel for 5 seconds or until the display goes into diagnostics. Then write down the E_ _ codes and the EE_ _ codes and then repost with the results. Turn the key off and restart the engine and the dash will return to normal. With the answers to those questions I can give you some things to check to solve your running problem. Bill