Missfire

I have recently bought three vehicles in the last two months the first two are completely dead in the water the third is my Jimmy and the person that bought it said that he had a battery in it drove it about twelve miles home parks in about eight to nine months ago has not had any time due to work to look at it he said something about it needs a new motor but then again it could just maybe be bad spark plugs or something that is causing the miss in the engine which is not bad at all it idalene it idles just missing every now and again the check engine light is flashing rapidly there sounds to be a little sputtering around the catalytic converter the engine has good power transmission seems to be shifting fine I crawled underneath it and the first thing I noticed was that the plate over the transfer case is not there so it's just exposed and there seems to be maybe you'd like some old fluids from something I do not know if it is coming from the transfer case or not but like I said the transmission seems to be shifting just fine also there is like a wine or almost a home and I thought to be the middle part of the car but I believe it's towards the rear end because I drove it about ten miles and went through some water and it is kind of a cool night and the rear end was hot enough it was steaming. Just needing maybe a some good suggestions on where to start