I only replaced the spark plugs (car was working fine before). Now when the car is idle the speed goes up and down and eventually turns off. The car works fine when driving at higher speeds. I also replaced the wires thinking it was that. I cleaned the air mass sensor, thinking it was dirty, and then even tried putting a new one in and still nothing. I triple checked the spark plugs, they are in (also put the old ones in and the same thing is happening). I also triple checked the spark plug wires to make sure they are going to the right ones. Please help!!
It's a Mercury Cougar 1999
It's a Mercury Cougar 1999