Just got a 2000 TJ sport 4.0, 5 speed. I've noticed that when its warm outside the engine doesn't have a lot of power, and vibrates at higher rpms (3k+). But when its cooler, usually nights and mornings, it revs much more smoothly without any vibrations and has much more power. I started to notice this when I'd go to the gym around 6pm (felt slow), but then id leave around 8pm and it felt like a completely different jeep on the way home.
Any ideas of what's causing this?
Any help is appreciated, thanks