I have a 1998 Ford Ranger XLT 4.0 V6 5 Speed and if I let it set for more than a day it's hard to start and when it finally does, it runs rough for about 3 to 4 minutes. I have little to no throttle response between gears but plenty of response when I put it in neutral. It takes forever to get up to speed unless I get into the 3.5k/4k range (used to shift around 2k/2.5k). I've had people tell me a variety of things including the IAC, the clutch, and the dual cats. I've always kept up on the maintenance on it and have had no trouble until now. Any input is greatly appreciated!

What do your spark plugs look like? Light tan and .050" gap is good, all plugs black is bad, white on one cylinder is bad (injector problem, also one plug black) .080 gap plugs are worn out. If all plugs black, look for a vacuum leak causing the MAP sensor to think you have the throttle wide open and dumping a lot of raw fuel. See answer "other models" thread on Mercury montego for details on checking vacuum. Also bad temp sensors will cause too much fuel, either air temp or water temp. Either of these seonsors should set a code, does your "check engine light" come on for 5 seconds when you turn the key on before you start it? If not, your check engine light is burned out, or missing on a 2nd hand car. If you have a light and a code, get somebody like an auto supply to read it.