wolfefin

I've got a serious cold start issue. When the weather is warm 70F+ at night, this is not an issue, but once the temp at night drops below 70, then this starts to happen and it's worse as the temp drops lower. When I get the in the car in the morning or after it's sat for a good while (like at work for 8 or 9 hours and the sun goes down), it takes forever to start the car, it just turns over and turns over and turns over, then it chokes a little bit and won't start but feels like it's starting to catch and finally after literally 5 to 10, sometimes 15 minutes of cranking the starter, it starts up. When I step on the gas it feels like it's going to stall and sometimes when I'm at a light it will feel like it's going to stall as well, but if I shift into neutral it seems ok.

I've checked the OBD and there are no warning lights, I've replaced the coolant temp sensor/switch. I've replaced the spark plug wires and distributor cap, all of which helped a minuscule amount, but, nothing has fixed the problem. I've noticed that when I run Shell Premium (93) it seems to be better than other brands like Hess or off-brand. Also, if I dump a bottle of octance booster in there, it seems to dramatically help the problem, but it still doesn't go away.

Any thoughts? Oh, and there's a big difference if I have it in the garage (unheated) or just sitting outside overnight. If I let it sit outside overnight, I'll literally run the battery dead trying to start the car.

Thanks for any help suggestions or thoughts ('92 300E, approx 210K mi)