misfire
 

car is a 99 gt
put my car in storage last fall, brought it out this spring and it ran perfect for a week then began to have a terrible misfire to the point of making it actually difficult to drive it. No check engine lite at all though. Thought it was a coil (still might be) but with the motor running I unplugged one coil at a time and noticed no major difference after each one was unplugged and replugged in. I did put new plugs in it last fall also and it ran fine after that. I am wondering if it may be somthing in the ignition? I dont know if these cars have one or not but maybe an ignition control modual? Looking for any tips or ideas of things to check before i throw the flag and take it to a shop to have it diagnosed.

Have you ever changed your plugs? Also did you treat the gas before putting it into storage?
If there is ANY water/condensation in teh tank, then it would cause the car to run poorly.

Yes I did change the plugs, Yes I put stabil in the tank with a full tank of gas before winter,