Engine is rough idling & hard to start

Start system. Most likely bad connection to Block temp sensor that sends data to ECU there are two sensors, one for the dash temp gague, and this one. I had this problem on 20 yr old car.
Found the correct sensor removed connector cleaned connector with contact spray and toothpick, scraped male spade connector on sensor to bright metal. Cleared codes. Instant start, just like new. Didn't have to change sensor as many claim needs to be done. Hope this helps. Sorry I don't know where yours is. Try a google image search for yr, Make model "Temp sensor" this one is probably near the back of the block. It has a "spring lock" to make sure it stays on. The dash temp is just a standard electrical connector.