I've had this problem before, but only when its really cold, like -10 or colder. But now its hardly freezing and its a long slow crank followed by one or two large thuds that make it completely stop cranking. I stop cause Im worried about bending a rod or something. Then it sounds like the starter is keeping it running cause ill have to pump the gas. After that its smooth sailing and starts after its warm are ironically faster than summer times. What is wrong here? its a 96' 4.0, just changed the oil, I put 10w40 like i always do, when I use 10w30 idling would cause low pressure. Any suggestions would help, its my only car and cant afford a another one.

could be your starter going out, and the problem only shows up when its cold

10w40 gets as thick as cold molasses in the winter time. Thats alot of extra resistance when the starter is trying to turn it over. If a thinner oil causes to have low pressure issues, look at saving up to fix that issue. In the mean time, id consider plugging in your block heater a couple of hours before you go to start it, it will help starting greatly.

Sorry, just re read your OP. If the issue is getting worse like you said, i check all the wiring from the batt to the starter as well. Corrosion at the terminals will also cause starting problems, epically when the oil is as thick as cold molasses.

Sounds like a dying battery to me... You're trying to start it and it cranks slowly and requires a second or two for it to start?

Thats a pretty sure sign of the battery not having enough power. I'm from Ottawa so it gets to minus 30 quite easily in the winter. My first upgrade with any vehicle is a 1000CCA not CA battery. Usually Optima or the top of the line motormaster(almost indestructible for a liquid battery)

As another poster said, use a block heater to keep the oil warm... its a good idea in any vehicle. As for the low oil pressure, if you wait for the vehicle to heat up it'll go away, you should wait for it to heat up anyway in all honesty.

well it sounds like you have more than one problem if you have to pump the gas try cleaning the tb and iac motor it sounds like its not working and then a new battery

Those "two loud thuds" concern me.

Have a buddy crank the engine while you try to isolate this.

As mentioned, be sure battery is up to the job (LOAD TEST IT), and of course the starter itself is suspect here. Be sure that all battery connections (terminals/posts) are SHINY clean.