So a few weeks back my Town Car started to do this. On occasion no matter whether the engine is hot or cold, whether the temperature outside is hot or cold, or the climate is damp or dry, for whatever reason sometimes it starts up and misfires violently, when you press the gas normally it doesn't want to accept it and it spews and stutters, and eventually dies. And there's the smell of gasoline from the engine. When it does this if you start and immediately keep on the gas a lot it runs, also if you were driving it, it hesitates, but evens out after a mile or so. It car run fine for two days, the run bad for a day and so on and so forth, not constant. Sometimes it also somewhat misfires on it's good days while running, sometimes rough, sometimes smooth, it looks like as if the system is rich after sitting for a bit longer or when it's running on idle or low rpms. I've got a spare part town car, and a limousine guy, that's a professional town car mechanic, done all kinds of diagnostics, live tests, no faults whatsoever, even after it misfires an dies, it's also next to impossible to catch live diagnostics while misfiring, because it just dies too fast. Checked what we could, changed what we could that could do this using spare parts from a 42k mile town car. Checked hoses, vacuums, anything a bit out of order we fixed or changed, fuel lines checked,, new fuel filter, fuel pressure is fine, had the maf sensor changed, the iac valve, temperature sensor, throttle sensor, did a tune up 5k miles ago (plugs, coils, etc) and ran perfectly. It just looks like it's running rich, gas mileage is horrible, like something leaking, or causing it to flood. thought to change the injectors, but they were newly changed when i bought the car 15k miles ago, and i mean if they were faulty wouldnt it be constant? I am out of ideas and it's been depressing, costing money and a lot of time with no results. It shows no signs of anything changed mechanically or electronically when it ran fine, nothing on the computer, when it runs fine or even a little misfiring but doesnt die, the live diagnostic feed shows everything is up to the level, all ok. the relays and amps anything related have been changed to new as well. It's probably my luck when the fault is probably a wire or something, rusted somewhat and it just does stupid things. I would appreciate any ideas thank you very much.