1998 mercury marquis check engine light came on and started running rough like bad gas expecially when accelerating all lights are ok runs good on the highway can you help ?

Without scanning it, it's possible the fuel pump is starting to go

Like the previous guy said you need run a scan of the computer to determine why check engine light is on it could be numerous things the scan of the computer narrows it down considerably

Scan, replace fuel pump relay, just because they go bad. It would show in scan.

I've worked on crown vic police cars for years and have had a few lose some pressure before total failure which created a rough idle and poor acceleration and it didn't always trip the engine light but it was rare, also check the age of the fuel filter.

Thanks guys! I just did want to show up at the shop and have somebody tell me I needed a new engine because I don't know much about cars My Marquis has been a great car and I have had minimal troubles over the years (15) Hate to think about replacing my car!!!