1996 Taurus Wagon 24valve DOHC idle problem

well i know this is posted somewhere, ok my taurus idles rough while in park, rpm fluctuates only when the car is cold, once i put he car in drive it drives perfect no problems at all, i do have the service engine soon light on, brought it to the mechanic dont remember codes but he said it was the cat and something to do with the egr.can anyone give me answers to this just wondering if anyone else had this problem and got it fixed.

Welcome to the forum!

It could be a vacuum leak, spark misfire, etc. You should be able to get the codes read at a local automotive parts store for no charge. Get the exact code number. You might be experiencing the somewhat common issue with the DPFE.

-Rod