1993 Grand Marquis - terrible idle.
My car has a couple serious problems. First of all, when it's been sitting for more than seven hours and I go to start it, it will want to die immediately when it starts. I have to feather the throttle for about six-seven minutes before it will idle without dying.
Secondly, it idles very roughly. When it's been sitting for ANY period of time, even just at a stop light, it will start to idle very roughly, slightly jerky. The idle will often go from slightly normal to badly low. When I start it after it's been off, even for a few minutes, if I try to set off with it without revving it for a couple minutes, I'll have basically no throttle response, and the engine will jerk badly. I have to mash the accelerator, and it will act like fuel isn't getting into the cylinders. Often, it will also make an alarming popping noise from under the hood. I'll have to keep the accelerate mashed for a good 5, 10 seconds before it will pick back up and smooth out.
What's the source(s) of my problems?