outlined engine light on, rough idle and surging as if it has a vacuum leak
running badly on 2000 Lincoln LS
This car is known to have bad ignition coils, and there is a Technical Service Bulletin for the 3.9 Liter engine. Unfortunately, they will replace on3 coil at time, not all 8 at once, with the newer, better design. I wish this car had a simple distributor and ignition coil, instead of 8 separate coil packs per cylinder. This is well known issue with this car. Low voltage in the coil, so you're firing on 7 cylinders out of 8
Mine was doing the same thing but i had the valves checked and 2 were dirty. They cleaned the rest of them and I haven't had any more problems. It costs around 400.00
If the check engine light is on, a shop can scan for trouble codes. If you're experiencing a surging idle it could be something related the idle air control (not sure if it's a valve or a servo). I think some Autozone's scan the codes for free but call around first. hope this helps
Look into EGR valve as well. Notorious for going bad.